DevTools: [CodeMirror] autocomplete for css supports hyphenated words

This patch refactors autocompletion functionality and moves vast majority
of autocompletion logic into AutocompletionController.

It additionally adds Autocompletecontroller an ability to define
word in its own way.

BUG=326525

Review URL: https://codereview.chromium.org/233303002

git-svn-id: svn://svn.chromium.org/blink/trunk@171289 bbb929c8-8fbe-4397-9dbb-9b2b20218538