Forward declaring fix: struct instead of class
Replacing remaining float weight types with E
Working on allocators
fixing remaining float weight type in main.cpp, not using dot exporters for a while...
reverting the allocator idea
Revert "reverting the allocator idea"

This reverts commit 9a020e81e8768b1e10ee6e59f5c43700f9a43c12.
Edge is now a class, returning references
vertices() and meightboursOf return vectors of const pointers
edgesBetween renamed to more descriptive weightsBetween