Pharo Wiki cleanup

In my attempt to make the contribution process for Pharo a bit simpler
I cleaned up the fogbugz wikis which where left a bit unmaintained.

There are now 5 important top-level categories:

Welcome Page:        https://pharo.fogbugz.com/default.asp?W41
Documentation:       https://pharo.fogbugz.com/default.asp?W69
Changelog:           https://pharo.fogbugz.com/default.asp?W2
Wishlist:            https://pharo.fogbugz.com/default.asp?W50
Responsibilities:    https://pharo.fogbugz.com/default.asp?W66

I removed old cruft that was documenting long gone features of ancient
pharo versions ;). I would be more than happy to get some feedback and
improve these websites gradually.

I will have a look.