Add -f/--force switch

Closes #16
Update Python to 2.7.5 and PyQt to 4.10.1
Add TortoiseGit

Closes #18
Add Windows 7 USB/DVD download tool

Closes #15
Add Steam to the catalog

Closes #19
Add "microsoft" installer type

Closes #17
Expand variables in URLs
Print package name and version upon installation