Cleanups and new features about corners and cells in partition and tableau

[sagetrac-numata]

The main goal of the patch was to add two functions namely arm_cells and leg_cells. On the way I found several bugs or inconsistencies:

Whereas the various cells methods returns the cells as tuple (i,j) Partition.corner used to return them as lists [i,j]. I changed them to return tuples. Various methods had to be fixed methods accordingly...

On the way I found that Tableaux.slide which uses Partition.Corner was modifying it's argument.

CC: @sagetrac-sage-combinat

Component: combinatorics

Keywords: Partition cells arm legs

Author: Numata Yasuhide, Florent Hivert

Reviewer: Anne Schilling

Merged: sage-4.4.2.alpha0

Issue created by migration from https://trac.sagemath.org/ticket/6655

[sagetrac-numata]

Attachment: trac_6655_partition_newfeature-ny.patch.gz

[hivert]

Description changed:

--- 
+++ 
@@ -1,4 +1,6 @@
-I add a following new feature in partition:
-a method returns a list of boxes in the arm.
-and so more.
+The main goal of the patch was to add two functions namely `arm_cells` and `leg_cells`. On the way I found several bugs or inconsistencies:
 
+Whereas the various cells methods returns the cells as tuple `(i,j)` Partition.corner used to return them as lists `[i,j]`. I changed them to return tuples. Various methods had to be fixed methods accordingly...
+
+On the way I found that `Tableaux.slide` which uses `Partition.Corner` was modifying it's argument.
+

[hivert]

Changed keywords from Parition to Partition cells arm legs

[hivert]

Changed author from NUMATA Yaushide to NUMATA Yasuhide, Florent Hivert