Allow setting a default Assembler

Despite a previous suggestion being marked as 'completed', there doesn't appear to be any setting for this anywhere, and how the game currently selects the assembler to use is inconsistent.

I often put an assembler on my ships - it's too useful not to have, as it allows you to recycle components and repurpose their materials in the field when salvaging. This, however, presents a problem - whenever I dock these ships to my station (using connectors, to rule out grid merging tomfoolery), it's luck of the draw as to which assembler the game will decide to use.

I'll find myself short of a specific component when building a new ship, and then find that the game's decided to use one of the ship assemblers with no upgrade modules over the assembler in the station with 4 speed modules. This is suboptimal.

What I propose is this:

Assemblers on static grids should take priority unless conveyor filters or connector trading mode would interfere, and of those, the fastest should probably be used. If all are equally fast, use the most power efficient. Adding a 'Is Main Assembler' setting, similar to how we can designate main cockpits for grids, will allow players to override this behaviour for that grid. Static grid assemblers will still take priority for as long as a ship is connected.

This would satisfy the vast majority of use cases, whilst still allowing the player additional control if desired.