Robustify the release process.

Review Request #2388 - Created June 18, 2015 and submitted

John Sirois
1684, 1685, 1686, 1687, 1688, 1706
ity, lahosken, stuhood, zundel
This addresses several issues:
+ Fixup detection of the current branch to work with OSX/bsd sed
+ Add a check for the git origin being valid for release tagging
+ Add a check for git configuration of the desired release pgp key and
  use this key to sign sdists as well.
+ Add a check that a proper ~/.pypirc is setup.
+ Add a check that the releaser has permissions to publish all packages
  to pypi.

Utility commands are also added to list packages and package owners and
the release documentation is updated with all prerequisites.

 build-support/bin/     | 207 +++++++++++++++++++++++++++++++++++++++++++++-----
 src/python/pants/docs/ | 122 +++++++++++++++++++++--------
 2 files changed, 281 insertions(+), 48 deletions(-)
Locally tested dry run still works with `./build-support/bin/ -n`
Also extensive local manual testing of the new checks.

CI went green here:
John Sirois
John Sirois
Larry Hosken
John Sirois
Stu Hood
John Sirois
John Sirois
Stu Hood
Eric Ayers
John Sirois
John Sirois
Review request changed

Status: Closed (submitted)