Added support for MODELGET, MODELDEL, SCRIPTGEL, SCRIPTDEL

[filipecosta90]

fixes #6, #11, #12, #13, #16
added methods:

• boolean setTensor(String key, Tensor tensor)
• boolean setModel(String key, Model model)
• Model getModel(String key)
• boolean delModel(String key)
• boolean setScript(String key, Script script)
• Script getScript(String key)
• boolean delScript(String key)

Adds TFLITE, and ONNX backends.
Also extended the coverage and kicked of a more detailed javadoc

[codecov]

Codecov Report

Merging #15 into master will increase coverage by 19.38%.
The diff coverage is 89.32%.

@@             Coverage Diff             @@
##           master      #15       +/-   ##
===========================================
+ Coverage   68.45%   87.83%   +19.38%     
===========================================
  Files           9       11        +2     
  Lines         336      518      +182     
  Branches       44       68       +24     
===========================================
+ Hits          230      455      +225     
+ Misses         86       31       -55     
- Partials       20       32       +12     

Impacted Files	Coverage Δ
src/main/java/com/redislabs/redisai/Tensor.java	86.66% <81.81%> (+36.66%)	⬆️
src/main/java/com/redislabs/redisai/RedisAI.java	84.88% <85.33%> (+11.62%)	⬆️
src/main/java/com/redislabs/redisai/Script.java	91.07% <91.07%> (ø)
src/main/java/com/redislabs/redisai/Model.java	92.15% <92.15%> (ø)
src/main/java/com/redislabs/redisai/Backend.java	100.00% <100.00%> (ø)
src/main/java/com/redislabs/redisai/Command.java	100.00% <100.00%> (ø)
src/main/java/com/redislabs/redisai/DataType.java	82.92% <100.00%> (+30.92%)	⬆️
src/main/java/com/redislabs/redisai/Keyword.java	100.00% <100.00%> (ø)
... and 4 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 71c110c...2fdbad9. Read the comment docs.

[lgtm-com]

This pull request introduces 2 alerts when merging f068d7a into cda15c0 - view on LGTM.com

new alerts:

• 2 for Dereferenced variable may be null

[filipecosta90]

@dengliming can you review the changes? WDYT of the additions?

[lgtm-com]

This pull request introduces 2 alerts when merging b091594 into cda15c0 - view on LGTM.com

new alerts:

• 2 for Dereferenced variable may be null

[dengliming]

@dengliming can you review the changes? WDYT of the additions?

LGTM :)

[filipecosta90]

@dengliming can you review the changes? WDYT of the additions?

LGTM :)

thank you =)

[filipecosta90]

@gkorland lets revise #18 first, and, if you agree, merge it. Then update this one from master and will automatically remove the formatting changes from this and the following PRs.
Also, with regards to the build failing it is due to the fact the latest redisai:edge image does not contain the already merged reply additions on modelget ( it should be a matter of hours for it to be propagated ).