Invoke jvm doc tools via java.

Review Request #2313 - Created June 3, 2015 and submitted

John Sirois
162, 1545, 1629
benjyw, ity, stuhood
This removes dependence on the `javadoc` and `scaladoc` binaries which
immediately opens up javadoc and scaladoc testing on Travis-CI.

For `javadoc` this is not so important today, since the new invocation
scheme requires a jdk for `tools.jar` which necessarily means `javadoc`
is present.  That said, it does set the stage for invoking javadoc
using the correct JDK based on the repo-wide or per-target JDK

 src/python/pants/backend/jvm/tasks/BUILD                      | 16 +++++++++-------
 src/python/pants/backend/jvm/tasks/             | 52 +++++++++++++++++++++++++++-----------------------
 src/python/pants/backend/jvm/tasks/              |  4 ----
 src/python/pants/backend/jvm/tasks/            | 51 ++++++++++++++++++++++++++-----------------------
 tests/python/pants_test/tasks/BUILD                           |  3 ++-
 tests/python/pants_test/tasks/ |  9 ---------
 6 files changed, 66 insertions(+), 69 deletions(-)

Ran a --combined gen locally via:

$ PANTS_DEV=1 ./pants doc.javadoc --open doc.scaladoc --open src/{java,scala}::

This opened up the 2 expected API doc pages.

The --no-combined cases are tested by the JarPublishIntegrationTest
already - now running in CI.

CI went green here:

John Sirois
John Sirois
John Sirois
Stu Hood
Ity Kaul
John Sirois
John Sirois
Review request changed

Status: Closed (submitted)