FileDB improvements
FileDB improvements

Added:
 - `Increment()` and `Decrement()` now supports arrays! To update many
columns per request, via:
   - `increment_array()`
   - `decrement_array()`

Fixed:
 - FileDB manager - " Update Table within model", via:
   - `update()` - again accepts `null`

dr-dimitru/indira,dr-dimitru/indira,dr-dimitru/indira,dr-dimitru/indira