Simplified schema and tweaked some bits

Removed obsolete ContextAmplifiers and SpecialGraphic attributes
Improved documentation and svg READMEs
Changed air corridor symbols to lines
Updated affected csv files
Changed the location of the geometry exception tags
Changed the descriptions on the gct tags
@abouffard - that graphic with the red arrows that said "reverse these 2 items was confusing? Perhaps look again: 

https://cloud.githubusercontent.com/assets/3090809/4918975/0549184e-64f6-11e4-8478-7e7afef8e7ed.png