rule for ProjectingJoin to Join and Project
fix BUG: calculate unnamed position using scheme of input
not from scheme of the Apply itself.
rules for clang to handle algebra from MyriaL and apply more cool optimizations!

in particular, we now remove unnused columns after joins
subset of datalog tests for clang ported to myrial

passing, too!
tweaks to raco.myrial.query_tests port for clang
skip query_tests port
include more clang aggregates
something
note about rules
allow for more than just Myria compiler to use myrial_test
flake
fakedb for clang that writes to files

not yet using much
remove cpp before writing