Extracted and tested the database interactions from ModifierSequence

[psh]

The goal of this PR is to simplify ModifierSequence and get decent tests around its database interactions.

To that end

• Database interactions were extracted into a ModifierSequenceDao
• Tests were added
• Classes that formerly called save() and delete() on ModifierSequence were updated to use a data access object
• Out of date comment in DBOpenHelper (reflecting pre-Dagger usage) was updated.

[codecov-io]

Codecov Report

Merging #1022 into master will decrease coverage by <.01%.
The diff coverage is 0%.

@@            Coverage Diff            @@
##           master   #1022      +/-   ##
=========================================
- Coverage     3.7%   3.69%   -0.01%     
=========================================
  Files         106     107       +1     
  Lines        5162    5166       +4     
  Branches      485     485              
=========================================
  Hits          191     191              
- Misses       4958    4962       +4     
  Partials       13      13

Impacted Files	Coverage Δ
...ns/modifications/ModificationsContentProvider.java	12.5% <0%> (ø)	⬆️
...ee/nrw/commons/modifications/ModifierSequence.java	0% <0%> (ø)	⬆️
...nrw/commons/modifications/ModifierSequenceDao.java	0% <0%> (ø)
...java/fr/free/nrw/commons/upload/ShareActivity.java	0% <0%> (ø)	⬆️
...n/java/fr/free/nrw/commons/CommonsApplication.java	27.65% <0%> (ø)	⬆️
...free/nrw/commons/upload/MultipleShareActivity.java	0% <0%> (ø)	⬆️
...ommons/modifications/ModificationsSyncAdapter.java	0% <0%> (ø)	⬆️
...in/java/fr/free/nrw/commons/data/DBOpenHelper.java	20% <0%> (ø)	⬆️

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[neslihanturan]

Hi @psh , can you please solve the conflicts, so that I can merge them. Thanks!

[psh]

There's a chance that merging the CategoryDao work will also conflict with this branch, so I'll wait until #1023 has merged before resolving the conflicts as it will save us doing things twice.

EDIT - conflicts resolved now that #1023 has been merged.

[neslihanturan]

Thanks @psh :)