tigefa4u projects Trac

Final touch to the ''System Information'' refactoring:
- the `env.systeminfo` is now an array instead of a hash; instead of an arbitrary order of the keys (or the meaningless alphabetical ordering), the entries are listed according to the sequence in which they were added.
- because of the above, care must be taken to store the version information only once
- on the About ''System Information'' page, adopted the same style as on the error page, for displaying the systeminfo table.
- ... and added version info for Trac itself

Do as we could get the version info from SilverCity. This only works if you built the package yourself with setuptools, for now. Also took the opportunity to fix #4031.

Follow-up to r4417: if the module_path is a directory, we need to examine all Distribution instances found and check whether the key matches the module name. A bit error prone, I wish there were a more direct and robust way to get the Distribution instance from a module...

Simplify version reporting for Python modules (refactor r4414-4416)

Put Pygments version information in the env.systeminfo

Follow-up to r4414, forgot that self.env was already available in a `Component.__init__` method.

Put Genshi version information in the env.systeminfo

Refactor some setuptools utilities from the admin module and move them into trac.util (get_pkginfo, get_module_path)

Show ''System Information'' in the About page (CONFIG_VIEW permission needed)

Small Python 2.3 compatibility fix