Islands in search results should be configurable

[Thomas Krause]

Search nodes that are too far apart to be shown in the same context (distance > context_left+context_right) normally creat islands ("..." is displayed between the tokens). The exact distance at which this happens should be configurable as one of three options:

    * context_left+context_right (current behavior)
    * NUMBER (e.g. 10 tokens)
    * none (never use islands, always give all tokens between hit nodes)

There should also be an option to display a control in the front-end which allows users to configure this in real-time. The admin can determine if this control is displayed/enabled depending on the corpora in the system (e.g. for legal reasons).

[Thomas Krause (krause)]

Support for "none" has been implemented. This has to be done in the service since the generated SQL already filters out nodes that match the condition or not (there no such code in the frontend).

Currently there is some global default configuration and you can create corpus specific configuration files in the service folder. Beeing able to change this behavior from the frontend would need more work and an expansion/complication of the service interface

For the fixed number things are a little bit more complicated. We don't know the token-order of the nodes at the time of the SQL-generation. Thus it's not clear howto implement this in a proper and consistent way.