Reformatted code to abide by mantid styleguide. Refs #3464
Apply and cancel button now function as expected. Refs #3464
Removed unused slots. Refs #3464.
Removed duplicate code. Refs #3464."

Accidently forgot to remove code when refactoring.
Checkboxes should not false on startup. Refs #3464.
Removed unnecessary methods related to error menu GUI. Refs #3464.
Fixed pie chart settings. Refs #3464.
Fixed percentile tab. Refs #3464.
Merge remote branch 'origin/feature/3464_fix_cancel_button_when_plotting'