During the last meeting, some problems were pointed out.
This commit should fix some of them.

Some UI bugs were discovered during a meeting, this is
a recommendation / example for new colors and fixing the bugs.

[Ticket: #219]

do not show category drop down when no tags available, fix style, change button background when selected

For keeping the active filter is now saved in a variable.

This reverts merge request !321

change questionwall icon, add person icon to questions, display answer, add questionwall button i18n