Remove obsolete docstring portions

Obseleted due to 38908cc
Hotfix bug in _close_all_but
Remove redundant os.sysconf call

subprocess.py already does exactly that call to try to set MAXFD
Use inherited pipes for IPC instead of STDIO

The main advantage being that STDIO streams can be redirected
independently without much effort.

Furthermore, this is very slightly faster in terms of startup time and
transfer speed when compared to _multiprocessing.Connection.
Put Connection related code into _libmadx_rpc

There are no changes in the actual code.
Minor cleanups
Make Madx.command a MadxCommands instance.

This is a fully backward compatible change.

The advantage is, that Madx.command now gives access to raw variants of
MAD-X commands, e.g.:

>>> madx.command('twiss', ...)
>>> madx.command.twiss(...)

Will just take all parameters, generically create a MAD-X command string
from them and issue them in the interpretor, without any special
treatment whatsoever.
Add more generic function mad_command

The new function should be used in favor of the now deprecated
_mad_command function.
Use the new simplified .command internally

This should be mostly backward compatible. One excepton is .match which
used _mad_command before.
Disable generation of unnecessary tempfiles

Also, change return type of Madx.match to not return the fit results
anymore, so it is independent of the filesystem as well. The new knob
values can be looked up with the Madx.evaluate method.
Remove obsolete functions in _madx_tools
Quote only 'file=' parameter
Merge pull request #52 from coldfix/inheritance-based-ipc

Use inherited handles for IPC with MAD-X backend
Merge branch 'improve-madx-command'

Conflicts:
	src/cern/cpymad/madx.py