master: add "use_default_node"
contrib/rrdcopy: use the shell cmd line for debug

This enables to copy-paste the debug line directly on the shell
command line.
contrib/rrdcopy: fix the comma separator
rrdcopy: the last value should not be used
doc: reworked install doc

    * Encourage packaged use
    * Tell more about the architecture
doc: adding a preface

Rewrite some parts of The Munin Guide.

The inspiration is *clearly* PostgreSQL's Book.
doc: fixed typo in preface
doc: build_ can be a symbolic link
doc: adding some preface

   * history
   * about
   * convention
   * bug report
doc: adding bug report section
doc: adding "getting help" section
doc: remove non-working search macro
doc: change settings
doc: fix typo in header
doc: adding "Where to Report" section
doc: adding page about plugin env
doc: fix table for env.rst
doc: adding the url to the PgSQL manual
doc: using cross doc ref
doc: add the tutorial skel