plugins: start implementing a new framework for plugins writing.

Munin::Plugin::Framework allows a much easier way to write new plugins
by abstracting the underlying protocol between node and master.

The idea is to have the plugins only declare what they want to have
displayed, eventually merging the code for configuration and
value-setting, and leaving it to the framework to generate the
configuration and fetch output.
procsys: implement a new plugin to replace entropy, open_files and open_inodes.

This new plugin uses the new Framework to create graphs for all the
sysctl-related data as a signle round-trip.

There is only one change compared to the previous plugins: open_inodes
produces a more meaningful graph of allocated and free inodes, rather
than the previous one that used a fake max value (as it was actually
the kernel's allocation).

Both open_files and open_inodes graphs now use areastacks instead of lines.
plugins: rewrite new multigraph plugins for using the Framework
procfs: merge load and uptime plugins.

The new plugin with the new Framework code makes it cleaner to just
have one place where most of the /proc files are read.
contrib/mnd: list command does not need ending space
master: use only the storable format for datafile
master/t: remove the plain datafile dump test
Merge branch 'storable-only' into devel
master/ProcessManager: avoid cpu hog when wait()
master/ProcessManager: adding a debug msg for reap
Merge branch 'procman-sleep' into devel
Merge remote branch 'origin/devel' into devel
Merge remote branch 'flameeyes/replacement-plugins' into devel