Convert 'file-patho to 'obj-patho with extra 'ftype argument.

This makes it able to find parent sub-trees and the like.
Add tabling logic to obj-patho.

This speeds up my test cases by ~1/3rd.
Adding first comprehensive example pldb query.

From a starting commit and a project name, show project information at
any points where the project directory has changed.

It's not pretty.

I want automatic fresh'd variables. And '_ ignorable / blackhole lvars.
Add indexing to 'r-commit field 'tree-sha.