Better integration of the mod Portal/faster mod loading time

[ukezi]

I have a few suggestions for the integration of the mod portal in the game:

• if you leave the mod download screen go back to the mod window and not reload the game directly
• implement the possibility to filter for versions as most of the mods are not yet compatible with 0.15
• implement dependency management so if you download a mod you get ask if you want to load the needed dependencies
• check game versions and mod versions on startup at the moment it goes like load game->update game->load game->update mods->load game. The polling of the game version is done anyway after startup and the polling of mod versions can be done parallel to loading from base.

To speed up mod loading time I have the following:
First how I think it works at the moment:

• the active mods are unpacked serial
• then the load order is created by building and serialising a dependency tree
• then the mods are loaded sequential.

How I suggest it should work:

• parallel unpacking,
• then creating the tree
• but loading it not sequential but parallel by opening a thread for each path.

I don't know if your data structure allows for parallel access but that should not lead to inconsistencies as the load order of mods not dependent on each other is not defined anyway.

By the way if two mods try to change the same thing in base how is determined whose change is the one in game? By load order, probably alphabetic?