Automatic file links

[koppor]

Activate following functionality:

1. Empty File tab:
   
2. Put "shafiee2016analysis.pdf" in file folder
3. Switch to other entry
4. Switch back
5. File is automatically linked:
   

"Old" behavior was that "Get fulltext" also searches on disk - but we removed that magic behavior somewhere

Yesterday, I got lost, because I did not know how the auto link feature works. It should be described in the documentation.

[ThiloteE]

Sorry, i cited wrong issue number by accident. The above pull requests are not related.