DRILL-221 Add license header to all files
DRILL-222 Update LICENSE and NOTICE files to incorporate dependencies correctly
DRILL-226: exclude dependencies with lgpl license
DRILL-223, add INSTALL.md and update README.md
DRILL-225: Add disclaimer to source release.
DRILL-224: Add md5 and sha1 checksums to source tarball.
Additionally, update pom to use local assembly plugin rather than apache release one so we can customize excludes to include .gitignore and sandbox.
DRILL-221: continued, add Apache header to poms.  Update checksum plugin to not fail on pom projects.
DRILL-221, part 3.  More license updates.  Automatically run Rat plugin with appropriate excludes.  Move Synth-log to sandbox until it is part of main mvn build to avoid weird RAT problems.
Update source assembly:
- to avoid packaging sandbox files.
- exclude .buildpath files from source release.