Removed MEZZ_LIB from a class that was defined entirely in the header.  This fixes UnitTests compilation on Windows.
Script binding updates.
Drafted up a structure for the upcoming UI manual.
A few doc fixes I missed in the last iteration, and more "bool" -> "Boolean".
Added some utility methods to the Rect class that will get the center of a particular axis.
Updated both the sizing and positioning components of layout strategies with new features.  Sizing by matching the other axis can now additionally be configured to use the unified dimensions for further customization.  Positioning offsets can now be configured to use previous offset, size offset, or no offset.
Finished the intial version of the Spinner widget.
Merge branch 'master' of github.com:BlackToppStudios/Mezzanine

Conflicts:
	Mezzanine/src/Scripting/Lua51/scriptbindingmainlua51.cpp
	Mezzanine/src/Scripting/Lua51/scriptbindingmainlua51unsafe.cpp
Post Merge script binding updates.