even faster inflation

This optimizes quite a bit how we introspect on the GomCursor to get the column<->property mapping. It also does away with the hashtable which was incredibly slow. We try to keep a GParameter array around because that is the simplest way still to inflate GObjects doing all their parameters at once (which is much faster than setting 1 by 1). The end of the array is stolen to place the repository as well to due away with extra allocations or copies when calling g_object_newv().