System info: Clicking on background shows system info again (fixes #2741).
System info: Properly change selected body when navtarget or hyperspace targets change and for unexplored systems (fixes #2743).
System info: Deselect navigation target when reclicking selected body.
Merge branch 'fix_system_info_view'
Save initial orientation of (rotating) frames. Bumps savegame.
Add missing initialization of m_oldAngDisplacement.
Determine if system is explored in Sector layer instead of StarSystem. Bumps savegame.
Merge branch 'save_initial_orient'
Merge branch 'pullup_explored'