plugins: fix typo (Muning::Plugin::HTTP)
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
/node.d/tomcat_threads.in: Fix if {'currentThreadsBusy'} go false when it is 0, and add a total value as 'currentThreadCount' so that the chart looks more readable.
Add a lower limit of 0 to postgres database size

This ensures that the graph always starts at 0 in stead of somewhere near the
smallest database size. This makes sure that database sizes are shown
proportionally correct.
Make the postgres_size_ y-axis behaviour configurable.
ignore 'INDIVIDUAL BUFFER POOL INFO' section in MySQL 5.5

If you set innodb_buffer_pool_instances to a value greater than 1 the status
will show a new section with details about each buffer pool instance.
I think the details a currently not needed so just ignore the section.