first pass at browse offset and match highlighting

Note there are TODOs (most notably the config file piece). 

Seeking input on:
* how to deal with the signature of alphabeticBrowse in VuFindSearch/Backend/Solr/Backend
* css styling (currently a blue box but if nothing else the color should change)
* is there a better way to figure out whether the result solr returns is an exact match? I'm actually fine with the rough comparison (uppercase, strip spaces) but if there's any easy and more precise way to tell I'd use that.