Add new time period filter 'from now'

Closes #569

See merge request arsnova/frag.jetzt!517

Resolve "Include answers to questions when searching"

Closes #436

See merge request arsnova/frag.jetzt!518

Merge branch '576-when-going-to-the-question-board-the-last-14-days-should-be-set-as-the-initial-time-span' into 'master'

Resolve "When going to the question board, "The last 14 days" should be set as the initial time span."

Closes #576

See merge request arsnova/frag.jetzt!515

Merge branch '567-when-a-filter-marker-or-time-is-active-the-corresponding-icon-highlights' into 'master'

Improve ux for active comment filters

Closes #567

See merge request arsnova/frag.jetzt!516

Users are now able to filter the comments from now. If an user has selected this option all comments disappear and only comments created from now will be displayed.
If the user selects another time period or the 'from now' option again, the period will reset so that the comments will disappear again.

Indicate with the color red if a filter is active. Also show a message if there are no comments with the active filters.

Resolve "Change filter options to favorites and bookmark in questionwall"

Closes #587

See merge request arsnova/frag.jetzt!512

Adds toggleable bookmark to question

Closes #577

See merge request arsnova/frag.jetzt!510

Add new time period 'last 14 days'

Closes #568

See merge request arsnova/frag.jetzt!508

Sort comments also if there are no active filters

Closes #572

See merge request arsnova/frag.jetzt!507