Turn off autocomplete on "Add collaborator" form

You have already created js autocomplete for that input, so it is good to turn off the browser autocomplete. If there are more forms that have custom autocomplete, this change should be applied to them, too.
Fixes issue #216

Added a div element to wrap the buttons so they are vertically aligned with each other. Also converted input and a elements to button elements as Bootstrap recommends: http://getbootstrap.com/css/#buttons-tags
Silenced compiler warnings
Merge pull request #221 from drwlrsn/master

Fixes issue #216
Merge pull request #220 from maliayas/patch-1

Turn off autocomplete on "Add collaborator" form
Merge pull request #228 from mcveat/compiler-warnings

Silenced compiler warnings
(refs #223)Display GITBUCKET_HOME on the system settings.
Upgrade scalatra-forms to 0.0.11.
(refs #196)Fire WebHook in merging pull request from Web GUI.