Declare embedding Order -> ambient number field
Trac #14989: Fix conversion of quadratic order elements to CC
Do not pickle caches of toric varieties
make sure simplex_points() works with immutable vectors, too
tutorial: Update URL
tutorial: typos
tutorial: update links
cython: patch: gdb output dir option
Replaced more private_variables by cached_method to enable pickling of ToricVarieties.
Refactoring ChainComplex as a Parent for Chains

* Various code refactoring to make it less copy&pasteish
* Slight change of conventions: ChainComplex._diff shall contain all
  differentials that are not 0x0. Before, we left out "obvious"
  incoming zero differentials that are 0xn.
Ascii art and more code refactoring for chain complexes
Chains (elements of chain complexes) and their module structure
finished refactoring the homology() method
Fixed super categories and all doctests
fixed bug in is_boundary()
Meredith Graph constructor

Conflicts:
	src/sage/graphs/graph_generators.py
Horton Graph constructor
Kittell Graph constructor
Markström Graph constructor
Sousselier Graph constructor