Added to the Main Menu a submenu for the Editors.
Changed menu_main() definition to allow restart or not of the background game
Cloned the Universe Editor to test and prepare for building a Map Outfit Editor. Also moved declarations of default values for stellar system from dev_uniedit.h to space.h.

Tip : when you add a new C source file, you have to add it to the Makefile.am list.
Began stripping down the Universe Editor clone to make a Map Editor.

Usage :
- Click on a system toggles it from the selection,
- Button "Save Map" saves the selection to saved_map.xml.

WARNING : still very partial WIP status !!!
- Lots of features still not functional or not even present,
- Some buttons redirected, but still not properly wired in,
- Lost view mouse-dragging, have to reintroduce it,
- And probably some other bugs and glitches I still have to find...
Restored viewport dragging.
Removed code behind the Open and Rename buttons. They are now empty.
Added the empty Save As button and spaced the buttons in 4 groups : Open, Operations, Save, Close.
Added a filename parameter to map-saving routine in dev_system.c, for further use in Save and Save As.

Changed Map Editor built-in names linked to buttons to test this feature : it works...
Adapted Universe Editor as it uses he same function.
Solved an assert crash on exit, prompted by having multiple maps with same name.
Added the 3 generated maps, and added them to tech.xml as well, so the dataset is consistent with the code.
Fixed a bug leading to menu_editors_close() being called twice. Changed Editors Menu dimensions to make it very distinct from Main Menu.
Added basic loading of Map Outfit into the editor.
Added 2 loading stages, 1 for map outfits, that will be useful when multiple map outfits will exist, and 1 for user data to be consistent.
Pushed constant OUTFIT_SHORTDESC_MAX from outfit.c to outfit.h, as it may be useful outside the Outfit module.
Merge branch 'origin/SoC-editors'

Conflicts:
	dat/outfits/maps/saved_map.xml
	naev-data/saves/Test.ns
	naev-data/saves/Test.ns.backup
Restored some saved data.