Remove the "lone pipe" exception in ShellCommand argument handling

As discussed in
<http://news.gmane.org/find-root.php?group=gmane.comp.python.buildbot.devel&article=10518>.
This makes it possible to pass a pipe as an argument, plus it makes argument
handling consistent between Windows and Unix-likes.
test for and consume warnings about legacy GSP
correctly set the path module for p4 tests on windows

This fixes #2916.
Merge pull request #1237 from djmitche/bug2916

correctly set the path module for p4 tests on windows
Merge pull request #1235 from djmitche/gsp-warnings

test for and consume warnings about legacy GSP
handle missing account properties for GerritChangeSource

* create a separate function to convert account properties
* make use of the function in all cases where the situation might take place
* update test cases

Fixes ticket:2918
update release notes
address pep8 errors
Merge pull request #1234 from SpecLad/remove-pipe-exception

Remove the "lone pipe" exception in ShellCommand argument handling
Merge branch 'bug-2918' of github.com:sa2ajj/buildbot into pr1241
_gerrit_user_to_author: fix codestyle to use string manipulation

Signed-off-by: Pierre Tardy <pierre.tardy@intel.com>
Merge branch 'pkg_fixes' of github.com:tardyp/buildbot into pr1240
some more fixes

fix the last resort version number to be 999.0
fix issue in codeparameter build (wrong dest dir for ace)
require distribute > 0.6.30 previous version have a problem:

 error: cannot copy tree 'buildbot_codeparameter/static': not a directory

Signed-off-by: Pierre Tardy <pierre.tardy@intel.com>