Contents of this patch:

Contents of this patch:
(1) Adds/revises documentation for rrd tune in rrd_tool.c and pod files.
(2) Moves some initialization code from rrd_create.c to rrd_hw.c.
(3) Adds another pass to smoothing for SEASONAL and DEVSEASONAL RRAs.
This pass computes the coefficients as deviations from an average; the
average is added the baseline coefficient of HWPREDICT. Statistical texts
suggest this to preserve algorithm stability. It will not invalidate
RRD files created and smoothed with the old code.
(4) Adds the aberrant-reset flag to rrd tune. This operation, which is
specified for a single data source, causes the holt-winters algorithm to
forget everthing it has learned and start over.
(5) Fixes a few out-of-date code comments.

git-svn-id: svn://svn.oetiker.ch/rrdtool/trunk@52 a5681a0c-68f1-0310-ab6d-d61299d08faa