Show all locations for spreadable equipment in summary view

[neoancient]

1. Adds a method to Mounted that returns all locations where the equipment is located. For most equipment, including weapons that are split between two adjacent locations, this is fairly simple. For spreadable equipment, which includes myomer and bulky armor/structure, but also equipment with multiple fixed locations like the partial wing, it's necessary to check all the critical slots.
2. Adds a method to Entity that formats the location(s) into a string for display. A second argument permits setting a limit to the number of slots that should be displayed without abbreviation. There are some special abbreviations for all-torso or all-leg equipment on Mechs.
3. Uses the new methods to show all locations instead of the single one returned by Mounted#getLocation in the MechView summary.

The fix for MegaMek/megameklab#869 is based on this.