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 branch 'improve-madx-command'

Conflicts:
	src/cern/cpymad/madx.py