#16 Metadata storage

[blindmatrix]

Not storing metadata in ram... or optional... I'm thinking three settings,

* Metadata in RAM, somewhat like it's implemented now
* Live metadata, that is, fetching data on the fly when requested (Easy on ram but heavy on the FS)
* mmap some sort of metadata structure on the disk, like a hidden .ushare-metadata file that can be refferenced...

Or a combination of the above,,, I'm voting for mmap or being able to select one in cfg