Dramatically improve LocalCollection sorting performance.

Currently, LocalCollection._insertInSortedList uses an insertion-sort type of insertion (which goes like O(n^2)).  This PR replaces it with a binary search type insertion (which goes like O(n lg n)).

The current method is very non-performant for large collections.  An `{{#each}}` block for a collection of 5000 elements dies incomplete after 15 seconds with the current method (and sometimes crashes Firefox).  With the binary search change, it renders in 5 seconds.