Data loader.

Added minimal dependencies of the data loader.
Minimal README for building.
.gitignore with files generated by sbt commands.

First pull request for rulextract.
Only 2 src files were added.
This can be compiled and run.
Files will be added incrementally and reviewed.
Note that I changed the input format: 1 file for source, 1 file for target, 1 file for alignment, 1 file for
provenance. The alignment is now in Berkeley format rather than acn format :)