[Request] Select Sprite to use from file

[VampireSeraphin]

Can we get an addition to MML lab where you can open a dialog window and select the sprite for your unit from the existing units, and it adds it to the mechset.txt local?

It would be much easier to have a small gui for this than continuously adding things to the localmechset manually.

[Dylan-M]

Since MML is a standalone product and run from a separate folder from MegaMek, a better solution would be to just create the line entry somewhere in the UI for easy copy/paste into the MechSet. Otherwise we would also have to allow choosing of the MechSet file to edit.

[VampireSeraphin]

Could you add a pop-up when you choose to load a unit from the cache to "use this sprite?" which edits your local mechset?

[HammerGS]

Completed with #1450