Update DRMAA Python version in eggs.ini to 0.7.6.

This version has better string handling and supports Python 3.
Re-add InterMine tools removed in 401ee23dcf2f70d4be0e975bb3e00a43ae1dfdd0.
Add empty_field validator to gtf2bedgraph.xml
Merged in daniel_blanchard/galaxy-central/daniel_blanchard/update-drmaa-python-version-in-eggsini-t-1402925026891 (pull request #421)

Update DRMAA Python version in eggs.ini to 0.7.6.
Fix popovers
Merge
Bugfix: Value error when specifying empty docker_volume param.
Thanks Andrew Stewart!
Allow Docker destinations to use --volumes-from option.
Enables certain kind of Docker-to-Docker job executions. Thanks to Andrew Stewart.
Fixes for Trackster and Circster, mostly around preference selection and usage.
Trackster: disable mousewheel scrolling for now until a better usage model can be created.
Add a very basic framework to the Tool Shed for creating a Galaxy flavor Docker Image that uses Bjoern Gruning's Galaxy Docker project.  This is a proof-of-concept that should be enhanced if kept.
Charts: Add comments, minor code clean up
Fix for grids, pack scripts
Fix trackster embedded grids
Fix unit tests broken with 4de240e.
Fix tool multi-run inside conditionals and repeats during state updates.
Fixes multirun inside of conditional, repeats if tool form state updated (e.g. because conditional param updated or repeat block added).

More tests - ugly tests - but tests.
Trackster: cleanup and better efficiency for 0932660.
Merged in BjoernGruening/galaxy-central-1/BjoernGruening/add-empty_field-validator-to-gtf2bedgrap-1403907588881 (pull request #427)

Add empty_field validator to gtf2bedgraph.xml