replace deprecated methods
Settings rename: captcha_default_challenge --> default_challenge
removed unused functions
Use Cache instead of state
removed unused language handling
better name for settings
fixed spelling and coding style error
remove prefixes from form elemnts, fix cache clear
Merge pull request #2 from md-systems/cleanup

Various fixes, removing of old and unnecessary code.
Rename readme.txt to readme.MD and remove old instructions from captcha_api.txt
Convert last form_state entries to objects
Fix typo
Fix form_state usage for image_captcha module
Try to downgrade phpcs because it has lots of odd errors
Remove unnecessary file as we moved preview page to controller
Introduced captcha plugin
New modifications
Make plugin captcha types work