Prefixed plugin manager service names with "VuFind\" as first step toward best-practice naming for global services.

Added ChangeTracker row object and accompanying test (but it doesn't work yet due to underlying limitations of ZF2).

Implemented SearchOptions view helper; added lots of ZF1-style search code that still needs to be ported over to ZF2.

Moved theme-specific view helpers inside VuFind namespace to avoid namespace profusion and to eliminate overcomplicated autoloader registration.