fakedb: implement projectingjoin delegate in myria join
rules.PushApply: push Apply into Projectingjoin when appropriate
Merge pull request #289 from uwescience/minor-fixes

Minor fixes
Merge remote-tracking branch 'origin/master' into bmyerz-myrial
clang_datalog_tests: style fix
platform_tests: make the class officially abstract

Explicitly specify the methods we expect a platform test to implement.
emitcode: style
DatalogGrappaTest: skip a little bit later

1) Implement all the abstract methods in DatalogPlatformTest
2) Skip as late as possible, that is, AFTER generating the code. This
   way we get better test coverage even if we cannot compile the code.
c_test_environment/.gitignore: ignore more intermediate outputs
Merge pull request #290 from uwescience/dhalperi-bmyerz-myrial

Dhalperi bmyerz myrial