Log some more things

[Capostrophic]

Sometimes it's difficult to guess the user's actions from openmw.log. I've added a bunch of extra log messages that should be helpful for debug.

• Message when a new game is started
• Message before a screenshot is made for a saved game
• Message when the actual saved game writing begins
• Message when saved game reading is started
• Message when saved game loading is started
• Message when the player character is teleported to the default cell because their current cell is unavailable

Exterior cell descriptions used in messages like "Loading cell", "Unloading cell" etc. now include the name if it's present or the region name if it's present or just "Wilderness" otherwise (localized GMST for the default cell name isn't available).