Removed ClickHandler class, set of code cleanings
Adding more smart GUI logic
Added format checker
Finished button disabling logic
Minor fix
List of operations is now loaded from ViewModel
Fixed JComboBox warning
Moved TODO list to the README file
Minor update to README
Now ComboBox keeps Operation
Now do Calculate on Enter
Cleaned GUI code a little bit
Updated test names
Removed if from the View, now it is even more dumb
Full code reformat with IDEA
Merge pull request #69 from kirill-kornyakov/mvvm-fixes

Polishing MVVM
rename core to Model
fix build.gradle
fix pakages
fix gradle build