Limit available planets in 'Sow cache' view

[bikerunner]

Change:

• the number of planets of a WH should be known and constant
• add this number to the WH table in database
• limit the number of listed planets in location and align lists to this number

Advantage:

• not possible to select wrong planets
• less listed planets may result in faster view processing

[Thricehappy]

Can we confirm this is closed now?

[bikerunner]

Can reopen if someone complains. Or create a new issue if something not working. Expect no issues at the moment.