Idea: Introduce a way to install mods from inside the game GUI interface.

[nani]

Currently there are two ways to install a mod: mod.io or a zip/pyromod file.
While the mod.io option is easy and direct the file ones is easy to get wrong and convoluted given that each OS platform has it own idiosyncrasies.

Idea: In the mod page, have an new button "Install from file" that opens the native OS explorer, lets you select the folder, zip or pyromod file. Once selected the pyromod engine should do the rest of the work and automatically copy the selected mod to the appropriate mod directory (this would solve the trouble with snap folders as many other hard to find OS dependent paths).

Optional features:
- It could also try to optimize the files while doing the installation
- It could also allow to "grep" a compatible url directly, eg: a github repo (even check for updates)
- Design a way to allow having multiple diferent versions of same mod (no all enabled at the same time of course :) ) and having it stated clearly in the GUI (currently is quite confusing)

This would allow a far easier installation, making obsolete all the problems of the kind "where to put the file" with an installation GUI for mods.