Half way done creating Expression Class
Edited some more files
Finished Expression class conversion. All tests pass.
Fixed bug unit bug
-Units still displayed in prevResult after unit selected + solve
Fixed bug where calc didn't update current UnitType
Implemented EditText for main text display (still bugs to work out)
-Backspace doesn't work fully yet
-Unit testing very broken for some reason?
-Cursor needs to disapear sometimes