Add OgreCameraSystem

See #14
Rename m_skyEntities to m_entities for consistency

All other systems just use m_entities.
Remove leftover code for static camera

We don't need that anymore.
Fix OgreEngine::update() to use RAII StateLock
Merge pull request #26 from Revolutionary-Games/14_camera

Scriptable Cameras
Merge pull request #27 from Revolutionary-Games/25_ogre_engine_update

Fix OgreEngine::update() to use RAII StateLock
Add id() method to Entity class

Mostly for internal use. May be exposed to scripts at a later
date.
Add any directory beginning with "build" to gitignore
Fix assertion in OgreSceneNodeUpdateSystem to not break release
Add scriptable viewports

See #24
Merge pull request #30 from Revolutionary-Games/24_viewports

Scriptable viewports
Simplify SharedData when updating a new working copy

This removes the callback mechanism and replaces it with a
version check each time SharedData::workingCopy() is called.
Add assertions and death tests for unlocked states

Terminate the program when trying to access stable or
workingCopy buffers when the state is not locked properly.
Merge pull request #33 from Revolutionary-Games/shared_data_improvement

Simplify SharedData when updating a new working copy
Merge branch 'master' into Physics