[Feature] Tag-based virtual file system like TMSU

[JediMaster25]

Create a virtual filesystem, like TMSU does, based on studios, performers and tags. To be able to easily browse the files based on the tags used in stash from other applications.

For example if a file had two tags (Indoors and Amateur), and no studio or performers. The structure would be:

Amateur
  Indoors
    file-symlink
Indoors
  Amateur
    file-symlink

The pros of rewriting TMSU is that studios and performers could be used independently of tags, and since it's written in go and uses sqlite it could easily be added to the main stash program without having to change too much code. I've made a script that imports the data from stash database to either the TMSU or Supertag databases. The problem is that I've decided to merge studios, performers and tags together. The main purpose of this issue is to be able to create a virtual filesystem that solves this issue, by making a different folder for studios, performers and tags.