Add new class for fetching single results in a background job.
Restrict query to one specific match.
Add increase/decrease buttons for context.
Disable decrease button when no context is left.
Use comboxes instead of buttons for changing the context.
Reloading query also takes the visibility status of the visualizer into account.
Provide an interface for changing context.
Remove old queries.
A single query for changing the context of a result does not executing the find
call on the rest api anymore. Now it is using the ordinary macht list of the
preceding query.
Allow custom values for context the single results.
Decrease distance between combobox and their caption.
The context of single results can be changed via simple select boxes.

closes #150

Merge branch 'closes_150' into develop

Conflicts:
	annis-gui/src/main/java/annis/gui/QueryController.java
	annis-gui/src/main/java/annis/gui/ResultFetchJob.java
	annis-gui/src/main/java/annis/gui/resultview/ResultViewPanel.java