Feature/metrics DB/SQL server

An evening hack.

To be clear: this supports any DB that https://github.com/mausch/FsSql supports.

The tests are being run with SQLite.

@karaaie - what do you think?

@mausch - The example problem comes when running Logary.DB.Tests
Optimisation ~20k/s:

 - Path -> separate table, PathId
 - Type -> known ints/enum, description on col
 - CorrelationId -> CorrelationType (type of data in next col) and CorrelationId (string approx 35 no of chars?)