git-archimport-script - 2nd iteration

Gave the code another pass. The code should be more readable, and make a bit more sense.

It now:
 - handles commit timestamps correctly
 - handles binary files correctly
 - uses parselog() to tell git-update-cache what's been
added/deleted/modified - much faster commits on large trees
 - gets the commit msgs mostly ok

In my immediate TODO:
 - handling renames
 - branches
 - incremental import

A bit further off:
 - file modes
 - merge detection

cheers,

martin