algorithms for trees and latex output

* several traversal algorithms
* some methods added for binary heap
trac #14498: some improvements on trees
trac #14498: Darij's review patch, to be applied ATOP of trac_14498-algorithms_trees-rebased.patch and trac_14498-tree-imps-dg-rebased.patch
trac #14498: more doc fixes
This is modified to redefine hardy z function. corrected some typos
Review patch on top of Rishi's wrapper changes to significantly improve the

documentation language and formatting. This also adds the wrapper to the
reference manual.
trac #8621 just minor details
algorithms for trees and latex output

* several traversal algorithms
* some methods added for binary heap
trac #14498: some improvements on trees
trac #14498: Darij's review patch, to be applied ATOP of trac_14498-algorithms_trees-rebased.patch and trac_14498-tree-imps-dg-rebased.patch
trac #14498: more doc fixes
trac #14498 whitespace removal and rebase on 6.1.beta5
Merge branch 'u/chapoton/14498' of ssh://trac.sagemath.org:22/sage into 14498

Conflicts:
	src/sage/combinat/abstract_tree.py
	src/sage/combinat/binary_tree.py
Merge branch 'u/chapoton/14498' of trac.sagemath.org:sage into 14498
further docfixes
oops one more
Trac #15707: convert power series to polynomial by truncation
trac #15707: doctest
added max_entry option to SemistandardSkewTableaux
allowing max_entry for tableaux of given size as well, and documenting the erratic behavior of this class (hopefully subject to later refactoring)