Change sw and te tokenizers for Mr.TyDi (#1727)

Note that we do not have language-specific tokenizers for sw and te, so we use whitespace, which is exactly 
the same as -pretokenized. Using -language xx is conceptually cleaner, but doesn't change results.

docs/regressions-mrtydi-v1.1-sw.md

@@ -15,7 +15,7 @@ target/appassembler/bin/IndexCollection \
   -input /path/to/mrtydi-v1.1-sw \
   -index indexes/lucene-index.mrtydi-v1.1-swahili/ \
   -generator DefaultLuceneDocumentGenerator \
-  -threads 1 -storePositions -storeDocvectors -storeRaw -pretokenized \
+  -threads 1 -storePositions -storeDocvectors -storeRaw -language sw \
   >& logs/log.mrtydi-v1.1-sw &
 ```
 
@@ -31,17 +31,17 @@ target/appassembler/bin/SearchCollection \
   -index indexes/lucene-index.mrtydi-v1.1-swahili/ \
   -topics src/main/resources/topics-and-qrels/topics.mrtydi-v1.1-sw.train.txt.gz -topicreader TsvInt \
   -output runs/run.mrtydi-v1.1-sw.bm25.topics.mrtydi-v1.1-sw.train.txt.gz \
-  -bm25 -hits 100 -pretokenized &
+  -bm25 -hits 100 -language sw &
 target/appassembler/bin/SearchCollection \
   -index indexes/lucene-index.mrtydi-v1.1-swahili/ \
   -topics src/main/resources/topics-and-qrels/topics.mrtydi-v1.1-sw.dev.txt.gz -topicreader TsvInt \
   -output runs/run.mrtydi-v1.1-sw.bm25.topics.mrtydi-v1.1-sw.dev.txt.gz \
-  -bm25 -hits 100 -pretokenized &
+  -bm25 -hits 100 -language sw &
 target/appassembler/bin/SearchCollection \
   -index indexes/lucene-index.mrtydi-v1.1-swahili/ \
   -topics src/main/resources/topics-and-qrels/topics.mrtydi-v1.1-sw.test.txt.gz -topicreader TsvInt \
   -output runs/run.mrtydi-v1.1-sw.bm25.topics.mrtydi-v1.1-sw.test.txt.gz \
-  -bm25 -hits 100 -pretokenized &
+  -bm25 -hits 100 -language sw &
 ```
 
 Evaluation can be performed using `trec_eval`:

docs/regressions-mrtydi-v1.1-te.md

@@ -15,7 +15,7 @@ target/appassembler/bin/IndexCollection \
   -input /path/to/mrtydi-v1.1-te \
   -index indexes/lucene-index.mrtydi-v1.1-telugu/ \
   -generator DefaultLuceneDocumentGenerator \
-  -threads 1 -storePositions -storeDocvectors -storeRaw -pretokenized \
+  -threads 1 -storePositions -storeDocvectors -storeRaw -language te \
   >& logs/log.mrtydi-v1.1-te &
 ```
 
@@ -31,17 +31,17 @@ target/appassembler/bin/SearchCollection \
   -index indexes/lucene-index.mrtydi-v1.1-telugu/ \
   -topics src/main/resources/topics-and-qrels/topics.mrtydi-v1.1-te.train.txt.gz -topicreader TsvInt \
   -output runs/run.mrtydi-v1.1-te.bm25.topics.mrtydi-v1.1-te.train.txt.gz \
-  -bm25 -hits 100 -pretokenized &
+  -bm25 -hits 100 -language te &
 target/appassembler/bin/SearchCollection \
   -index indexes/lucene-index.mrtydi-v1.1-telugu/ \
   -topics src/main/resources/topics-and-qrels/topics.mrtydi-v1.1-te.dev.txt.gz -topicreader TsvInt \
   -output runs/run.mrtydi-v1.1-te.bm25.topics.mrtydi-v1.1-te.dev.txt.gz \
-  -bm25 -hits 100 -pretokenized &
+  -bm25 -hits 100 -language te &
 target/appassembler/bin/SearchCollection \
   -index indexes/lucene-index.mrtydi-v1.1-telugu/ \
   -topics src/main/resources/topics-and-qrels/topics.mrtydi-v1.1-te.test.txt.gz -topicreader TsvInt \
   -output runs/run.mrtydi-v1.1-te.bm25.topics.mrtydi-v1.1-te.test.txt.gz \
-  -bm25 -hits 100 -pretokenized &
+  -bm25 -hits 100 -language te &
 ```
 
 Evaluation can be performed using `trec_eval`:

src/main/resources/regression/mrtydi-v1.1-sw.yaml

@@ -6,7 +6,7 @@ index_path: indexes/lucene-index.mrtydi-v1.1-swahili/
 collection_class: MrTyDiCollection
 generator_class: DefaultLuceneDocumentGenerator
 index_threads: 1
-index_options: -storePositions -storeDocvectors -storeRaw -pretokenized
+index_options: -storePositions -storeDocvectors -storeRaw -language sw
 index_stats:
   documents: 136689
   documents (non-empty): 136689
@@ -48,7 +48,7 @@ topics:
 models:
   - name: bm25
     display: BM25
-    params: -bm25 -hits 100 -pretokenized
+    params: -bm25 -hits 100 -language sw
     results:
       MRR@100:
         - 0.2610

src/main/resources/regression/mrtydi-v1.1-te.yaml

@@ -6,7 +6,7 @@ index_path: indexes/lucene-index.mrtydi-v1.1-telugu/
 collection_class: MrTyDiCollection
 generator_class: DefaultLuceneDocumentGenerator
 index_threads: 1
-index_options: -storePositions -storeDocvectors -storeRaw -pretokenized
+index_options: -storePositions -storeDocvectors -storeRaw -language te
 index_stats:
   documents: 548224
   documents (non-empty): 548224
@@ -48,7 +48,7 @@ topics:
 models:
   - name: bm25
     display: BM25
-    params: -bm25 -hits 100 -pretokenized
+    params: -bm25 -hits 100 -language te
     results:
       MRR@100:
         - 0.2847