Add test for checking generated .tac file

It checks that .tac file is valid Python script by exec()-uting it with
mocked globals imports, such as twisted.application.service.Application
and buildslave.bot.BuildSlave.
Then it checks, that Application was created and stored in global
variable "application" (as .tac specification requires); checks that
BuildSlave created with passed arguments and attached to application.
Add tests for basedir containing quotes, spaces and backslashes

Quotes test failing with master Buildbot.

In one of the older Buildbot releases I tried to create slave on Windows
end ended with invalid .tac file due to something like this:

  basedir = 'C:\basedir\'

Looks like this is fixed in master, but adding test won't hurt.
Fix handling basedir with quotes
Add tests for invalid --umask and --allow-shutdown options

Currently fails.
Handle invalid --umask and --allow-shutdown options
Add test for handling special characters in all options fields

Currently fails.
Fix options fields writing in .tac file
Write "log-size" as numeric, since it's always integer
fixed PEP8 violation
Merge branch 'slave_tac_check_and_fix' of git://github.com/vrutsky/buildbot
create slave: use OS specific path in messages
use OS specific paths in unit tests
Merge branch 'fix-utests-win' of https://github.com/elmirjagudin/buildbot
Master-side source steps support patches. Fixes #2098
Merge branch 'bug2098-squash' of git://github.com/srinupiits/buildbot
SVN source steps mode=export support authentication. Fixes #2463
skip 'stop slave' test on windows

Windows does not have os.kill() function, which is used
in the tested code path. Skip the test for now.
PyFlakes: fix handling of syntax error
Merge branch 'master' of git://github.com/kviktor/buildbot
Master side source checkout steps support retry option. Fixes #2465, #2357