Annotate meta data for db plugins

Provide a MetadataFrom setting to name columns whose content is to be
added as metadata to the data collected.  Similar in usage to the
ValuesFrom setting.
curl_json plugin: avoid cache aliasing by using all fields instead of the final two

The following two keys

  Key workers/*/requests
  Key workers/*/apps/*/requests

can both lead to type_instance's of say

  0-requests

which would alias in the cache.  If, instead of just the final two key
name components, we use all of them it would lead to these

  Key workers-0-requests
  Key workers-0-apps-0-requests

which would not overlap.
version-gen.sh: Ensure only collectd repository versions are used

When cross compiling in hosted environments using RPM,
the extracted tar-ball can be located in a parent .git repository.

The version-gen.sh script will then take the version number from
this repository as if it represents collectd.

This can be even more erroneous when the version returned is non
numerical and breaks the build

Signed-off-by: Kieran Bingham <kieran.bingham@st.com>
Make sure that "PIDFile" option cannot be set when command-line option "-P" was used. (Fixes #553)

The "PIDFile" value from command-line option "-P", which should take
precedence over any "PIDFile" value from configuration files, could be
overwritten if a configuration file contained the "PIDFile" option.

We introduced a new global variable "pidfile_from_cli" which will be set
to 1 when the command-line option "-P" was detected and the
"global_option_set" function will only set the "PIDFile" option if
"pidfile_from_cli" is 0.
Merge pull request #553 from Whissi/issue_553

collectd ignores command line argument "-P"
Merge pull request #408 from radford/curl-json-cache-aliasing

curl_json plugin: avoid cache aliasing by using all fields instead of just two
Merge pull request #321 from mwongatemma/db_meta_data

Annotate meta data for db plugins
Merge pull request #427 from kbingham/version_fix

version-gen.sh: Ensure only collectd repository versions are used
ReportByCpu and ValuesPercentage are now independant
ReportActive false now actually does as advertised

Change-Id: I93d9c36778253373c05b4efada5b082147656d89
Merge pull request #679 from ccin2p3/f/cpu-percent-vs-ticks

ReportByCpu and ValuesPercentage are now independant