Changed the way hints are processed in js (#53).

To allow to enable the new hint modes g;{MODE} it's better to filter the hint
texts without using xPath. So we filter only those items that are actual valid
and don't need to query the whole document for matching items.
On the other side, do we have more control about how the pattern matching is
done, case sensitive, matching word beginnings or fuzzy search or what ever.
Used a little bit more object orientation for hints (#53).
Use relative font size for hint labels.
Increase z-index of active hint label.

This allows to see the label while stepping though the hints via <Tab> event
if hint label overlaps each other.
Little code style changes in hints.js.
Fixed none left hint mode if no hint is available (#53).
Added new hinting filter behaviour to man page.
Save the active hint object instead of idx.

This make some things easier.
Keep active hint focused if it's still valid (#53).

If a hint is focussed and later filter will keep it valid, the hint also keeps
focussed.
Reset hints number filter on new text filtering (#53).
Change variable name in hints.js.
Simplified the config stuff in hints.js.
Leaf hint mode if hint prompt is not valid.
Merge branch 'master' into hinting-g-mode
Added extended hint modes g;X (#53).

These hint modes are taken from pentadactyl and works like the other hint
modes, accept that the hints are not cleared after a hint was fired using a
numeric filter.
Don't hint images that are surrounded by link (#53).
Set z-index on hint container instead of every item.
Merge branch 'hinting-g-mode'

Conflicts:
	src/hints.js
Fixed typo in word prompt.