Added grind rule to build PNaCL Android RSA module
Removed some logs
Added PNaCL binaries for Android RSA
Added nacl module to .gitignore
addressed review comments
Merge remote-tracking branch 'upstream/master' into 1480-build-nacl
Merge pull request #1484 from dinhviethoa/1480-build-nacl

Integrated NaCL in the build process of Spark