added transactions around restapi users collection checks #378

In restapi.cpp we look at admin.system.users to do auth.  These needed
transactions to work properly.

closes #378
added WebInformationCommand to encapsulate webUI=true cmds #378

This should make it easier to distinguish, and now we have sane defaults
for things like beginTransaction.
Merge branch 'restapi-1.0' into restapi-merge

Conflicts:
	src/mongo/db/dbcommands_generic.cpp
	src/mongo/db/restapi.cpp
removed extra webUI param from plugin/loader cmds #378

Don't need these anymore since we added WebInformationCommand.
Merge branch 'restapi'