added ability to invoke Jill through APIs

Just like jack, jill was invoked by spawning a separate process for each
conversion. With this CL, we also support invoking it using their public
API.

Set  USE_JACK_API=true and USE_JACK_LOCATION=/path/to/jack/and/jill/jars
to use the new facility.

Change-Id: If2ce63ca73779ed1766b923c9d7cd9cf26bfe97f
7 files changed