collectd: Fixes bug-13074, create collectd.d directory

collectd: Fixes bug-13074, create collectd.d directory

- As requested in bug 13074, create a collectd.d directory to enable any addon definitions
   to be created.
- Added include statement in conf file to load everything that is stored in the collectd.d
   directory.
- collectd.precache and collectd.thermal have been left in their original locations
- Removed the arm section in the initscript as only aarch64 is now used.
- Modified the lfs to create the collectd.d directory
- Removal of collectd.custom file as this was the previous way to define custom collectd
   profiles but would have been overwritten by any update of collectd.
- Update of rootfile to take account of new path and removal of collectd.custom
- Tested out in vm testbed with Core Update 188 and all existing graphs were still created
   and updated. From my evaluation the changes have not affected anything.
- The creation of the collectd.d directory now allows users to add their own desired
   profiles but also if it is decided that an addon should be included in the processes
   graph, or if a new graph for addons is created then profiles for that addon can be
   placed in the collectd.d directory and will be automatically included by collectd.

Fixes: Bug13074
Tested-by: Adolf Belka <adolf.belka@ipfire.org>
Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>