Greatly extend and improve the test file for adaptors (#67)

- Add concept checks for the alterable, extendable, erasable
and clearable adaptors.
- Add test cases for modifying the underlying graphs through adaptors
whenever it is possible.
- Check the conversions between Node, Arc and Edge types.
- Add more test cases for the adaptor-specific functions and maps:
enable(), disable(), status(), forward(), backward(), CombinedArcMap,
CombinedNodeMap, ResidualCapacity etc.
- Use checkGraphIncEdgeArcLists() to simplify the test cases for
undirected graphs.
- Add test cases that use static graph structure (GridGraph) with
several adaptors combined.
- Add comments for the test cases.

 #! /usr/bin/env python

 import sys

 from mercurial import ui, hg

 from mercurial import util

 util.rcpath = lambda : []

 if len(sys.argv)>1 and sys.argv[1] in ["-h","--help"]:

     print """

 This utility just prints the length of the longest path

 in the revision graph from revison 0 to the current one.

 """

     exit(0)

 u = ui.ui()

 r = hg.repository(u, ".")

 N = r.changectx(".").rev()

 lengths=[0]*(N+1)

 for i in range(N+1):

     p=r.changectx(i).parents()

     if p[0]:

         p0=lengths[p[0].rev()]

     else:

         p0=-1

     if len(p)>1 and p[1]:

         p1=lengths[p[1].rev()]

     else:

         p1=-1

     lengths[i]=max(p0,p1)+1

 print lengths[N]