Fix loading a savegame when some of its content files were disabled

Fixes #1380
Respect CMAKE_INSTALL_PREFIX in the global openmw.cfg

Fixes installing to /usr/local (Bug #1378)
Properly handle exceptions when saving the game

Add message boxes when an exception occurs while loading or saving the game
Fix large size_t being truncated to int
Change CharacterManager to use list instead of vector

Solves a crash when deleting all savegames of a character due to mCurrent being invalidated
Ignore raycasting shapes for weapon collision tests

Fixes dead bodies being in the way when they shouldn't.
Re-enable collision when an actor is resurrected
Show wallpaper when loading a savegame
Fix for dereferencing past end of mGuiModes.
Rewrite journal GUI quest index

 - Use quest names as identifiers, not quest IDs. This ensures that quests with different IDs, but the same name (e.g. A2_4_MiloCaiusGone and A2_4_MiloGone) are merged properly, as they should.
 - Switch display from BookPage to MWList. Handles word-wrapping and scrolling properly.
 - Fixes a bug where the quest index would not be updated when opened.
Fix a crash on exit when projectiles were active
Fix overlapping text in SpellWindow when the window is too small
Rewrite journal GUI topic list to use MWList
Small optimization to ESM::Variant
Fix loading ESX files cleaned with testool (Fixes #1382)
Add missing hasItemHealth for lockpicks/probes (Fixes #1385)
Revert "added changed reference tracking for cells"

This reverts commit f4334da42ec0076c073aed1a3aec6a4a17f1ba5a.
fix for bug #1369
Cycle with equipped items if all slots are occupied (Fixes #1395)
Fix not reacting to quit request while video is playing