Optimize and clean-up form history

Optimize and clean-up form history

Switch from g_file_test() to g_access()

Initialize suggestions once the DOM is ready and only once

No need to handle WEBKIT_WEB_NAVIGATION_REASON_FORM_RESUBMITTED

[JS] Hide suggestions if search pattern was cleared

[JS] Human usable up/ down navigation in the suggestion window

Reusing a single suggestion window introduced a regression.
Suggestions were filling into the wrong editbox if there was more
than 1 on the page.

Some comments fixed and style clean-ups

Removed dead code