More bugfixes and improvements

[sturnclaw]

• Fixed a (potential) issue where the main menu doesn't know how to find the ship its displaying if the name of the model doesn't exactly match the name of the shipdef.
• Amended some validation warnings/errors to shuffle around their severity.
• Fixed a rogue trailing quote in the Tolisay faction name.
• Fixed Error in debug view when tab object has no label #6022.
• Fixed Game crashes on hyperjump with star field density set to 0 #5880.
• Fixed System Editor does not load position within the sector. #6012.

As is traditional for my microfix PRs in the weeks leading up to release, this is getting merged quite quickly.