Added :state to missing elements

Added :state to check, edit_box, edit_line, list_box and radio as
discussed in issue #430. Includes corresponding rspec tests.
Converted tabs to spaces

Converted tabs to 2 spaces in new state.rb file.
Refactored :state into separate module

Moved :state in separate Common::State module.
Merge pull request #431 from rjack1201/master

Added :state to missing elements