Better nosetest build folder naming

[stonier]

Windows failing to build genmsg which uses

catkin_add_nosetests(${PROJECT_SOURCE_DIR})

and it falls all over the C:\ prefix to the path. This led to finding this bit of code:

• Was it actually intending to strip the source directory and not the binary directory? I can't see the reason you'd want to strip the binary directory and stripping the source directory makes it more convenient for introspection.
• This regex replace code is quite a bit simpler for removing prefixes
• Provides a name when ends up with the empty string (could maybe choose a better name?)
• Also replaces colons with dots to avoid problem windows path characters.

[dirk-thomas]

Can you please test the branch cleaner_nosetest_target_names, verify that it does what you wanted to achieve and report back?

[stonier]

👍 - branch changes work fine.

[dirk-thomas]

New pull request pending: #382