Eternity Engine game configuration: it's again possible to set the floor and ceiling brightness independently from the sector brightness

Eternity Engine game configuration: fixed a problem where the Friendly and Dormant flags were not correctly pasted in Doom format.

Eternity Engine game configuration: fixed a problem where the 3DMidTex flag was not correctly pasted in Doom format. Fixes #606

Eternity Engine game configurations: added support for arbitrary map names in the default testing parameters

Negative vertical patch offsets are now handled correctly based on the game configuration. Fixes #561

Added fixes for the stuck thing checker for the Eternity Engine configuration (thanks for hawkwind3). Fixes #551

Eternity Engine configuration: moved portal related sector flags to the portals tab of the sector edit form

Probably fixed probable I/O race condition when loading images.
Fixed Visual mode stuttering due to floating point precision degradation when running the editor for several days without restarting (internal timer is now reset when saving the map or creating a new one).
Fixed, Nodes Viewer, cosmetic: Nodes Viewer window position was reset after pressing the "Rebuild Nodes" button.
Added Eternity Game configurations by printz.
Updated ZDoom_ACS.cfg (CheckClass).
Updated ZDoom ACC (CheckClass).