Support inherited DAO methods

[joshuatam]

Can support similar implementations:

import 'package:floor/floor.dart';

abstract class BaseDao<T> {
  
  @insert
  Future<int> insertModel(T model);

  @update
  Future<void> updateModel(T model);
}

@dao
abstract class ItemDao extends BaseDao<Item> {
  // Other Queries...
}

Closes #258

[codecov]

Codecov Report

Merging #281 into develop will increase coverage by 0.01%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##           develop     #281      +/-   ##
===========================================
+ Coverage    81.27%   81.28%   +0.01%     
===========================================
  Files           51       51              
  Lines         1383     1384       +1     
===========================================
+ Hits          1124     1125       +1     
  Misses         259      259

Flag	Coverage Δ
#floor	81.28% <100%> (+0.01%)	⬆️
#floor_generator	80.61% <100%> (+0.01%)	⬆️

Impacted Files	Coverage Δ
floor_generator/lib/processor/dao_processor.dart	100% <100%> (ø)	⬆️

---

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 39e3be5...15b00fb. Read the comment docs.

[vitusortner]

Thanks for your contribution! I've added tests and support for inheriting DAO methods that are defined in interfaces (done by using the implements keyword on a class) and mixins.