python-sage work without cliquer patching (#14349)
module_list: add cl.c to cliquer.so sources (#14349)
also provide sage.env.SAGE_ETC
unhardwire runtime paths in various cases

- singular shared object
- maxima init (also s/exists/isfile/)
- share/graphs
- share/conway_polynomials
- share/reflexive_polytopes
- gap data dir
- python include dir
- numpy include dir
- singular include dir
- factory include dir
take care of sage-maxima.lisp in old makefile
Merge branch 'runtime_paths' into python_sage_build
Merge branch 'reduce_cliquer_patching' into python_sage_build
python-sage fix qepcadrc path
python-sage: move files around, turn into templates

(this is to help git keeping track)
python-sage more explicit import/include paths

intended to work with -I<parent_directory_of_'sage'>
python-sage s/lib(gap|ecm).so/libsage\1.so/

lib(gap|ecm).so already exists and confuses autotools

RECHECK: module_list
python-sage: comment on header hack
python-sage: module_list

- BLAS
- conditional extensions
- include paths
- m4ri extra_compile_args
python-sage: build system

- BLAS, BLAS2 check
- generate setup.py, module_list.py
- AC_ARG_VAR
- am_check_python_headers
- AM_DEFAULT_EXT globally (?)
- common makefile
  - dependency tracking for cython files
  - some automake global flags
  - some recursive targets
- add all makefiles to AC_OUTPUT
- header checks
  - cliquer/cl.h
  - flint
  - libgap
  - ..
- create dependency dummies for cython
- AC_AUTO_HEADER (reduce cruft in gcc-calls)
- checks
  - jinja2
  - whether cython supports dependencies
  - cliquer/cliquer.h
- as_ac_expand
python-sage: Makefiles
python-sage gen_interpreters.py
python-sage: fix module bound macros
python-sage: move pyx->pyxx (#15039)

(also changing module_list and references)
python-sage: .gitignore update
python-sage: env.py