Preserve navmeshes + AIN nodes when install mods PR

[Alystrasz]

Currently, when installing a mods PR, we install only mods from said PR, meaning navmeshes/AIN nodes are those from the PR repository, and not those from navmeshes repository.

Solution:

(thanks @Zanieon for the insight!)

[GeckoEidechse]

Could we offer navmeshes as a separate mod upstream? That would also resolve the issue and shipping them separately would significantly reduce update size for Northstar updates as well ^^

[Alystrasz]

Let's just copy/paste that mod/maps directory from main profile, shall we?