Xenballoond

- [FEATURE] Add support for the 'soft_max_mem' config parameter and XenBus
path {memory/minmem} to control the maximum allowed size.
- [FEATURE] Allow to override minmem from XenBus path {memory/minmem}.
- [OPTIM] Removed all calls to xenstore-exists(8) to avoid a few useless
forks and improve performances (maddingue).

- [BUGFIX] Fixed a few bugs (nagius).
- [FEATURE] Make the emergency mode more aggressive (nagius).
- [FEATURE] Improved the cpu and uptime stats (nagius).
- [DOC] Document all configuration parameters in the manual page (maddingue).
- [DIST] Added init(8) script for Debian- and Red Hat-based distributions (maddingue).
- [DIST] Added MANIFEST and Changes (maddingue).

- [CODE] Refactored the whole program (maddingue).
- [CODE] The configuration file is now a pure static .INI file (maddingue).
- [DOC] Added semi-generated manual page (maddingue).
- [DIST] Shaping the whole thing in a standard Python distribution (maddingue).