Fix button widths on formula editor keyboard and add regression test

add regression test for button widths on formula editor keyboard

fix button widths in formula editor keyboard

Add assertion error message for FormulaEditorKeyboardTest/testLayout

Change FormulaEditorKeyboardTest/testLayout: all weights in a row have to add up to 1

fix number type in assertEquals

get views dynamically

remove comments
Merge pull request #904 from StefanTischler/master

#668 fix formula editor button widths and add regression test
experiment