add class to track versions of programs
add other comparators implemented in terms of less-than
add ability to query current variable value from directory (or it's parent)
Add ability to query the compiler version
add version check to know if we can emit deps directive
fix up setup
start generalizing extraction of interesting things

when user says "Compile( xx, yy, zz, ww, ... )", want to extract /
unpack whatever lists, tuples, direct things into a concise list of
entities by type. This is a start of that
checkpoint work on adding chained tools and recrafting flag passing
fix version check
add check for really old git version which didn't have a number in it
checkpoint implementing new-style compile
checkpoint work on refactoring variable usage
fix typos
finish chained tracking support for libraries
switch to allowing multiple output files on one target