UK Controller Plugin 2.3.0

- Fix bug where dependencies were not properly downloaded if they were in the file list but not on the file system.
- Fix bug where RATSU intention code was not properly displayed.

Overhaul of the Hold Manager, with the following changes:

- Hold managers are now synced between controllers, so aircraft added to the hold by one controller will be reflected to others.
- Only the controller currently tracking an aircraft will be able to assign it to a hold.
- Clicking on the aircraft's callsign in the hold display window will popup the hold selection menu.
- Clicking on the aircraft's cleared level in the hold display window will popup the cleared level selection menu.
- Aircraft now "stack" properly in the hold if they are at the same level.
- If an aircraft is within proximity of a hold, with another aircraft assigned to the hold at the same level, the extra aircraft will be displayed in the hold display until the potential conflict is vacated. This will be indicated by a green box around the hold level.
- Changed "blocked" hold levels to from a hash mark to a slightly-lighter background colour to aid readability.
- Added an options button to the top of each hold display, this triggers the hold parameters dialog where custom level-boundaries for the hold may be set.
- Removed hold profiles as they made the UI unnecessarily complicated. All hold display data is saved per ASR.
- Possible places to hold are now defined internally by Navaids, rather than designated holding fixes - this will allow arbitrary fixes to be added quickly for big events.