Trac 14990: implement algebraic closures of finite fields
more methods to algebraic elements
add examples to .cardinality()
fix the parent in pth_root and pth_power
allow no argument for .algebraic_closure()
remove the optional name from algebraic_closure examples
rename _coerce_2 to _to_common_subfield; cosmetic changes
tiny optimization for _to_common_subfield and implementation of
is_finite.
fix comparison of pseudo-Conway polynomial trees
add a _latex_ method to the elements
rename/fix change_level(); new doctests
matrix2.pyx: no special case for finite fields in F.algebraic_closure()
do not check twice for irreducibility
implement three more methods
cosmetic improvement to nth_root()
Merge branch 'develop' into ticket/14990

Conflicts:
	src/doc/en/reference/finite_rings/index.rst
Trac 15040: added error handling to logicparser.py and added functions, implies(), get_trees(), get_formulas(), consistent() and valid_consequence
Merge branch 'develop' into ticket/14990

Conflicts:
	src/sage/rings/finite_rings/finite_field_ext_pari.py
	src/sage/rings/finite_rings/finite_field_prime_modn.py
fix doctest: finite field homset now has unique representation
Merge branch 'develop' into 14990-closure_finite_field