Fixed deadlocks in Recording API

[ksuprynowicz]

This fixes deadlock in Interface and in Assignment Client due to Recording API calls. Earlier all Recording script API calls happened on main thread using BLOCKING_INVOKE_METHOD, which is fine for ones that don't do anything script engine-related, but will cause a deadlock when script value such as script callback is copied or accessed. I added a recursive mutex to all calls to be sure that it's thread-safe.