Get parameter defaults from frei0r.
Switch to indexed propery names for frei0r params.

Properties supplied by frei0r param name are supported for backwards
compatibility.
Merge branch 'frei0r-metadata'
Improve frei0r metadata with sanitized defaults.
Add input pointer checks to mlt_properties (SF-191).
Fix Segmentation fault at exit by calling av_lockmgr_register( NULL );