Added vsvim_useeditordefaults setting

This setting allows users to specify that VsVim should default to Visual
Studio settings even if there is a VimRc file present.  Without this
setting the presence of a _vimrc file would prevent Visual Studio
settings from ever taking hold.  Users were forced to either delete the
_vimrc or move all of their Visual Studio settings into the _vimrc file.
Word motion on blank line was causing exception

The word forward motion on a blank line was causing an unhandled
exception to be thrown.  The logic that accounted for ending on a new
line and backing up over blank lines wasn't accounting for the case that
the caret line was itself blank.  Instead it backed up over it and tried
to create a SnapshotSpan with the points out of order (end before
start).

Fixed it to never back up over the caret line
Fixed a bug in the memory leak tests

It turns out a major source of the unreliablity was the
IKeyBindingService implementation.  It was looking for commands in the
created IVimBuffer *after* it was closed by the test method.  This
caused it to add event handlers after the fact and hence caused the
hooks to be added back in which were already expected to be freed.
Released 1.3.3 Patch 2
Merge remote-tracking branch 'origin/staging'