Start with transitioning basic category code to Cython
Merge branch 'public/categories/over-a-base-ring-category-15801' of git://trac.sagemath.org/sage into ticket/16296

* 'public/categories/over-a-base-ring-category-15801' of git://trac.sagemath.org/sage: (25 commits)
  #15801: doctests for CategoryObjects.base_ring + docfix in Modules.SubcategoryMethods.base_ring
  #15801: Initialize the base ring for module homsets
  Trac 16275: fixes for the previous commit; btw its title should have read: removed sage.modular.abvar.homspace.Homspace.__reduce__
  This is handled as well by the generic of Homset.__reduce__ method, and the latter takes care of setting check=False as needed.
  #16275: update ticket number in the comments
  #16275: added doctest illustrating an unpickling where Hom is called on an uninitialized parent
  #16275: trivial commit to use format
  Other changes: - Use ``X in category`` for sanity checks in Hom - More doctests
  #16275: A bug fix for Homsets between simplicial complexes over some higher category (_Hom_ was not checking its input).
  Trac 15801: proofread Travis's comments + minor doctest improvements
  Fixed Sets.Algebras().
  Fixing up doc and some other minor things.
  Trac 15801: added warning about not yet fully implemented subcategory tests
  Trac 15801: fixed ReST typo
  Trac 15801: improved subcategory and containment tests for categories over a base ring category
  Trac 15801: fixed typo in doctest
  Trac 15801: use a group algebra rather than a polynomial algebra in an example to keep it interesting
  Trac 15801: fixed recent missing import
  Trac 15801: little fix in polynomial_default_category, and update doctests involving categories of polynomial rings
  Trac 15801: update thematic_tutorials/coercion_and_categories.rst w.r.t the full initialization of matrix spaces
  ...
Some cdef in _sort, _sort_uniq and join
Merge the latest commits of branch 'ticket/10963' into ticket/16296

* ticket/10963: (25 commits)
  Trac 10963: degraded a bit a newly added cross-link to work around 'make doc-clean; make clean' failure
  Trac 10963: proofread Darij's edits
  Trac 10963: Fixed crosslinks
  documentation edits to clarify that super_categories should not contain anything twice
  Updated Sage version to 6.2
  sage-cleaner: fix rm_rf on OS X
  Updated Sage version to 6.2.rc2
  fix grep
  skip checks if we do not use the system pkg-config
  fix indentation
  avoid potential race when creating pkg-config
  fix search path, add tests
  export variables
  fix permisions, reviewer patches
  fallback to system pkg-config if necessary
  Update top-level README.txt and installation guide to describe the new directory structure.
  reviewer changes
  updated readme
  #16196: rebased to #16232
  adding a doctest to make sure 13624 is fixed
  ...
Remove closures in C3_sorted_merge by something faster, and make it cpdef
Merge branch 'u/SimonKing/ticket/16309' of git://trac.sagemath.org/sage into ticket/16296

* 'u/SimonKing/ticket/16309' of git://trac.sagemath.org/sage:
  Fix parsing of Cython function definition in sageinspect
  Fix sage_getargspec on static methods of Python classes in Cython code
Merge branch 'ticket/16309' into ticket/16296

* ticket/16309:
  Get source code for nested classes defined in Cython files
Fix one test (new import location)
Improve canonicalize_axioms by using a faster container for axioms
Stick with Python for category/category_with_axiom, use cythoned helper functions
Move most of Category.join to category_cy_helper.pyx
Fix Category.join with as_list=True. Fix doctests in sage.categories
Add doctests, remove a not used function
trac #16398: Cleaning the Graph documentation index
trac #3912 tentative of using lstlisting in latex doctests
Merge branch 'u/SimonKing/ticket/16296' of trac.sagemath.org:sage into public/categories/speed_improvements_category_with_axiom-16296
Very minor review changes.
Removed get_all_axioms.
Replaced get_all_axioms with all_axioms in doctests.
Merge branch 'u/ncohen/16398' and 6.3.beta6

Conflicts:
	src/sage/combinat/designs/incidence_structures.py