Split key handling function into "specialized" functions

Split key handling function in XfdashboardFocusable into "specialized" functions for 'key-press' and 'key-release' events. This make handling repeative 'key-press' event easier and cleaner (code), e.g. for moving selection when key is pressed and hold pressed. 'key-release' is only called once when pressed key is released.
Fix loading scalable images by icon name

Load images by icon name with scaling at requested size. If file to load is a bitmap it should already be at right size but if is scalable image (svg) is was loaded as a too small bitmap and then scaled resulting in an ugly image but now should look good and "right-scaled".

Conflicts:
	data/themes/xfdashboard/xfdashboard.css
Fix CSS file cherry-picked from master branch

CSS in branch 0.2 does not understand @constants and @-functions so remove these lines.
Bump version to 0.2.2