split MWWord::World::update into multiple functions
updated MWWorld::PhysicsSystem::getFacedXXX functions

 * changed the names and return values to be consistent
 * made the distance to search a parameter
 * change the distance returned to world units instead of percentage of query distance
update MWWord::World to track distances while performing occlusion queries.

This allows checking the activation distance against what is stored in GameSettings. Experimentation suggests that a second distance is required for NPCs.
Factored faced object lookups into MWRender::World

 * Renamed MWWorld::World::getFacedHandle to getFacedObject.
 * Changed it to return an object pointer
 * Updated clients to use return object directly.
added a separate activation distance for NPCs
added option to override the activation distance

The command line option '--activate-dist <int>' can be used to override
the in game activation distance.
Create a separate scenemanager for each CharacterPreview instance
include members of BSAArchives in Ogres resource indices
reworked DirArchive to improve performance

Replaced old file index with a simple map. The map works by storing the
file's relative path with path seperators normalized, and in lower case if
not in strict mode. Incoming searches are normalized in the same way then
the name is searched in the map. The value in the map is the original full
path to the file which is then used to created a ConstrainedDataStream. In
addition to changing the index, the commonly used Archive methods are
implemented so that they don't fall back on the default FileSystemArchive
implementations.
Merge remote-tracking branch 'blunted2night/issue_460'
Merge remote-tracking branch 'blunted2night/bug_495_v2'
silenced some warnings
Merge remote-tracking branch 'wheybags/master'