Massive refactoring

This commit does some massive refactoring of the Salt source:

  - reclass and all adapters have been changed to support the distribute
    (setuptools) entry-points interface, while they are also runnable
    directly (using `/usr/bin/env python`);

  - reclass and all adapters now use exactly the same approach to
    configuration (sensible defaults + config file + command-line
    options), but inventory/nodeinfo is properly parametrised (e.g.
    top/pillar for Salt);

  - the documentation has been updated accordingly;

  - defaults and constants were factored out into common modules.

Signed-off-by: martin f. krafft <madduck@madduck.net>
diff --git a/README.Hacking b/README.Hacking
index b70be09..028f842 100644
--- a/README.Hacking
+++ b/README.Hacking
@@ -12,6 +12,9 @@
 
   python setup.py develop
 
+Now the reclass script, as well as the adapters, will be available in
+/usr/local/bin, and you can also invoke them directly from the source tree.
+
 To uninstall:
 
   python setup.py develop --uninstall
@@ -37,4 +40,4 @@
 
 If you have larger ideas, I'll be looking forward to discuss them with you.
 
- -- martin f. krafft <madduck@madduck.net>  Wed, 03 Jul 2013 20:02:39 +0200
+ -- martin f. krafft <madduck@madduck.net>  Thu, 04 Jul 2013 22:20:20 +0200