convert_map_from() should only store weak references
Similar to coerce_map_from, the detected morphism
should be stored only in a weak dictionary, not
in a list.
Use a proper WeakValueDictionary for number fields
Replace Map.(co)domain by constant functions, remove ._(co)domain
Add generic copy of maps. Fix copy of elements.
Replace _(co)domain everywhere
Keep a strong reference to the codomain of PrecomposedAction
Keep strong reference to codomain of weakened coerce maps
Keep strong reference to domains of *registered* coercions
Let SchemeMorphism inherit from Morphism, not from Element
Copying of PolynomialBaseringInjection and FormalCompositeMap
Change SchemeMorphism back (to cope with a Cython bug),
copying the new code from sage.categories.map.Map
Add docs to SchemeMorphism
Generic copy method for maps, using _update_slots
Use a cdef _codomain, since the codomain is strongly refed anyway
Add doctests
Add warning to string repr of weakened maps.
Implement copying for *all* kinds of maps.
Merge branch 'master' into ticket/14711

* master: (216 commits)
  also remove untracked directories after an aborted import patch
  trac_interface: encode fields with utf-8 as well
  sage.dev: don't textwrap during doctesting
  patch.py: deal with hg's silly copy commands
  SageDev: fix pull doctest
  SageDev: remove branch keyword from pull
  fix doctest errors in SageDev.push
  remove (now) bad uses of SageDev.pull
  remove unused garbage
  dumb down pull to fix it
  don't abort ticket editing on nop push
  remove last reference to download command
  fix dev scripts in emacs shell
  remove , from my name
  fixed missleading error message for trac authentication error
  [FIXUP] 5.13.beta2: update git specific files
  5.13.beta2
  5.13.beta2
  fixed import statement for the commandline interface
  fix doctest failure from bad merge conflict resolution
  ...

Conflicts:
	src/sage/schemes/generic/morphism.py
Merge branch 'master' into ticket/14711

* master: (61 commits)
  [FIXUP] 5.13.beta4: update git specific files
  5.13.beta4
  5.13.beta4
  [FIXUP] 5.13.beta3: update git specific files
  5.13.beta3
  5.13.beta3
  Trac #15402: fix eint1() precision
  #14706: fix visibility of symbols for built-in libintl.
  remove reference to sage/misc/hg from docbuild
  #15268: let ncurses build on Solaris.
  #14706: Move previous install of R on OS X.
  Trac #15268: Add new ncurses config file to .hgingore.
  Trac #15337: Speed up ulp() method, add epsilon() method, add field arguments
  Trac #15397: fix bug in product of Schur functions by using lrcalc to complete calculation
  Trac #15098: couldn't resist fixing a typo
  needless bikeshedding
  #14706: Add $SAGE_LOCAL/lib to LDFLAGS.
  #14706: update to 3.0.2.
  Trac #13951: fix bug in local height
  Trac #15098: remove import of is_* in matrix.all
  ...
Minor fixes, that became needed since #14711 was not merged quickly
enough
Address the "check" keyword of scheme morphisms by name, not position
Merge branch 'develop' into ticket/14711, resolving conflicts with Trac
12217

* develop: (274 commits)
  Updated Sage version to 6.1.beta1
  Run Jmol from current directory
  bug fix : importing BooleanPolynomialRing at the top-level prevents sage from starting
  Trac #15445: review + broken doctests
  trac #15054: reviewer's comments
  Update installation guide for installation with OS X Mavericks
  also changed the order of options, as requested in comment 1, and few other minor edits
  Updated Sage version to 6.1.beta0
  removed isinteger option in delsarte_bound_hamming_space, as (mathematically) incorrect.
  gen.eval() documentation: mention that f(x) == f.eval(x)
  Allow default arguments in closures
  Mention that PARI supports conversion from tuples
  Document sig_error()
  Trac #15403: knapsack's docstring doesn't document an useful feature
  Trac 12217: correctly handle division by zero
  Update signals section of developer manual
  Revert parts of 67a76032fda3ee140c3bc52422020ef722cbee52
  #14912: fix leaking print statement when running doctests.
  #14912: Fix two doc tests concerning unique representation.
  trac #14912: more changes, hopefully adding a systematic intro to factories
  ...

Conflicts:
	src/sage/rings/fraction_field_FpT.pyx
Reviewer changes. Mostly formatting.
Now using _internal_coerce_map_from.
Initial attempt at _internal_coerce_map_from_() method.

Conflicts:

	src/sage/structure/parent.pyx