- plugins: allow hinticons for plugins

Default is <plugin>_hint.png; an entry 'hinticon=another_name' in
<plugin>.cfg overrides this; use icon in plugindir first; if not found
use icon in one of the other wellknown neutrino icon directories.
- - plugins: use hinticons for plugins in usermenu and pluginlist
Merge remote-tracking branch 'cool-cst-next/cst-next'
M. Liebmann CFrameBuffer: Fix paintIcon() for use icons with full path