Replaced all __XYZ_H guard-blocks with EDA_XYZ_H

Because underscore is a reserved prefix -- kudos to Manu343726
Removed NON_CONST_VARIANT hack from util.h

clarified CVector iterator
added bounds-checking for Vector/CVector iterators
added find() variant that returns non-const iterators
added non-const value() variants to iterators
Fixes bugs introduced in previous comit re vector iterators and deque
Initial version of unit tests, still redefining iterators
First working tests for linear containers
Rename test.cpp to demo.cpp, updated scons file