initial commit of volume.c
Added configuration for autotools
removed unused var plugin_volume
Set default size from GB to bytes.
changed LIBADD to reference variable BUILD_WTH_LIBLVM2APP_LIBS
added the use of df_complex and changed fprintf to ERROR for error
messages.  Also changed variable names to follow recommended standard
from the website.
Returning lvm_errno on error
Corrected typo
Added logical volume size metrics
added missing comma to AC_CHECK_LIB for lvm2app
changed symbol check for lvm2app
Changed data type from vg to vol_group and lv to logical_vol to be more descriptive
volume plugin: Fix a couple of issues from the code review.

* Use df_complex as data type.
* Submit LV sizes and "free", but not "total" and "used".
* Fix error handling; don't use variable if it is NULL, remove calls to
  exit().
Removed un-needed files

Signed-off-by: Florian Forster <octo@collectd.org>
Changed plugin from volume to lvm

Signed-off-by: Florian Forster <octo@collectd.org>
AUTHORS, README: Add Chad and the LVM plugin.
Merge branch 'cm/lvm'

Github: #291
Signed-off-by: Florian Forster <octo@collectd.org>