Merge pull request #77 from dubhater/fixes

Fixes
Clarify frame properties
VFM: Free the input nodes in the destructor
VDecimate: Free the input nodes
VDecimate: Rearrange the code a bit

I think it's more readable, and it will make it easier to modify frame
properties, now that frames are returned from a single place.

The output and the speed are the same.
VDecimate: Load overrides from createVDecimate

All other initialisation is there.
VDecimate: Add metrics output
VDecimate: Adjust frame durations when they exist