Setup to link against matching Urho3D library version. Fixes #152.

Existing CMake build scripts has been configured to generate different Urho3D library name based on active build configuration. However, when finding and using the library itself, the scripts did not differentiate the two versions and could cause problem with wrong version of the library is being erroneously linked against.
Increased the threshold for justifying a threaded Octree raycast. Exposed PhysicsWorld::Raycast() to Lua.
Added a warning when an UnknownComponent is created.
Fixed mismatching scene savefile names in Lua examples.
In XML mode, allow editing of UnknownComponent attributes as strings. This is as far editing them can go without adding extra data to the whole XML serialization. Closes #149.
Removed unnecessary include.
Added external projects/links documentation page.
Travis CI: API documentation update at 2014-01-26 12:40:59 UTC.
[ci skip]
Web-sync at 2014-01-26 21:24:05 +0800.