Add mutex lock on config defaults
Implement a copy of data for the prerender thread to prevent prerender (not-main thread) and the data manager (main thread) having access/operating on the same data.

This stops another cause of occasional segfault at the expense of speed. It may be preferable to move all prerender functions back into the main generate thread
to escape the thread->export->copy->import->thread behaviour here. Will need profiling/benchmarks for the views.
Copy and paste from Table Views