[Configobj-develop] some enhancements

[Jack K. <kj...@gm...>]

Hi all,

attached is my version of configobj.py modified from configobj 4.3.2. It
includes the following changes:

- pickling support
- list interpolation. For example:
    k = 1,2,3
    h = %(k)s
    g = interpolate %(k)s into a string
    f = interpolate, %(k)s, into, a, list
    l = %(k)s,
 can be interpreted as the following:
    k = 1,2,3
    h = "1,2,3"
    g = "interpolate 1, 2, 3 into a string"
    f = interpolate, 1, 2, 3, into, a, list
    l = 1, 2, 3
- environment variable interpolation. Eg, %(PATH)e  gives the value of the
PATH environment variable
- "section path interpolation". Example:
  %(a/b/c/k)p interpolates the value of key, k, of subsection c of
subsection b of subsection a of the current section.
  .. and . and absolute path can be used as well:
  eg,  %(../a/b/c/k)p      %(/a/b/c/k)p
  '/' can be escaped with \/  and . can be escaped with \.

- double % escapes interpolation, ie. %%(abc)s gives %(abc)s literally
- added two methods, lookup and fetch, to Section, to search a key upward
the tree.

The changes should be clear if you compare the configobj.py 4.3.2 with the
modified version.
I hope these features might be useful to others as well.

Thanks all!
Jack