expand COM registration to HKCU (instead HKLM only)

[dornech]

For environments where user do not have admin access it is beneficial to be able to register Python COM Servers for the current user only. I think this is specially a benefit for portable Python environments using great WinPython distribution.

I think of an additional switch: --system: register for HKLM --systempref: register for HKLM, if no authorization register for HKCU --user: register for HKCU default mode is system (as today)