Version the file associations

[marekr]

@nickoe

It might be a good idea we change the file associations a little.
Right now it works like this:

.css registry entry -> links to kicad.css registry entry
kicad.css registry entry has info on the icon and open command

What many programs do

.css registry entry -> links to kicad-5.0.css registry entry
kicad-5.0.css registry entry has info on the icon and open command

The link is just a name reference to another set of registry keys. And so many programs "version" the link. Useful for side-by-side installs because the .css registry entry can have multiple links set and the user picks one as default.

My problem is I think we should only do Major.Minor for the extra info.....but we only have a string PRODUCT_VERSION passed to the nsis compiler which could not be a real version number.
I've also seen the git 8 character hash used too for "nightlies", you can't use the full hash due to character limits in the name.

Its extremely easy to do however, since I added
!define REG_VALUE_NAME "KiCad"
and it just needs to be tweaked to include version on compile ;)