Tool for extracting historic motor positions from database dump

As a developer / instrument scientist, I would like to be able to easily recover archived motor positions from mysql dumps. .mysql files is in ASCII so we should be able to only extract the small subset of data relevant for restoring the motor positions instead of dealing with the full, unwieldy, multi-gb archive file.

### Acceptance Criteria
- [ ] We have a script that easily lets you recover historic motor positions from a .mysql dump file

### Extra Information
_Why it is needed?_
This has hit us on POLREF and CRISP in the past where we tried to restore a motor position from a point in time before a mysql dump was performed. The workaround we used in these cases was to reimport the mysql dump and recover the motors, but this takes a long time (problematic if work on the instrument is impeded by this) and may not be possible if the disk does not have enough space to import the mysql data.

_Where required files/links are_
This could be integrated into the existing `restore_motor_positions.py` in `/inst_servers/master/scripts/` so you can optionally pass in a file with historic motor positions instead of pulling it from the live database