Remove support for KMeleon devbuilds and add (somewhat hacky) support for IE devbuilds

We cannot actually compile the builds so they are expected to be already in the directory, merely generating the listing and update file is automated. The current scripts aren`t meant for builds with multiple files per version so I use a rather unconventional hack - "-x64.msi" is declared to be the package suffix and I deduce the URL of the x86 download from the x64 one. I also replace the built-in filesizeformat template filter by own custom one - the former doesn`t work correctly on my machine for some reason (it currently works on the server but might stop working on update).

[Felix Dahlke, 2013-06-19 11:43:01]

LGTM