store.h: Removed very outdated comments in the documentation.
store: Store "data-store" information alongside metrics.

A metric data-store describes how to access data (e.g. time-series) of a
metric.
core: Introduced the concept of time-series.

A timeseries describes one or multiple sequences of data-points where each
data-point is a timestamp and a value.

A new type of plugin, "time-series fetchers", has been introduced to access
time-series information from arbitrary data-stores.
plugin: Added sdb_plugin_fetch_timeseries().

This function fetches a time-series from a named backend data-store using a
previously registered "time-series fetcher" callback.
timeseries: Added sdb_timeseries_destroy().
timeseries: Added 'data_names_len' field.

Else, a user cannot tell how many different sequences are stored in a
data-series.
store: Added sdb_store_fetch_timeseries().

The function fetches a time-series for a specified host's metric and
serializes it into a JSON buffer.
frontend/parser: Added support for the 'TIMESERIES' command.

Syntax is: TIMESERIES <host>.<metric> [START <datetime>] [END <datetime>]
frontend: Let CONNECTION_QUERY support 'TIMESERIES' queries.
integration/simple_query.sh: Test another failure mode.
collectd::unixsock: Store metrics instead of services.
Moved backends from src/backend/ to src/plugins/backend/.
store: Fixed JSON-serialization of time-series data.

Typos caused the end-time and all values to be treated incorrectly.
timeseries: Fixed timeseries_destroy().

Correctly access all information indexed by data_names_len and make sure not
to access array members if the array is NULL.
timeseries: Added sdb_timeseries_create().

This function allocates a time-series object and pre-allocates the data array
based on size information passed to the function. All memory is initialized to
zero (except for the length information) such that the object contains valid
(but mostly useless) information.
timeseries::rrdtool: Added a plugin to fetch time-series from RRD files.

Obviously, the plugin requires librrd. The configure script checks for librrd
using pkg-config.
collectd::unixsock: Record the, configurable, time-series store.

The new config options 'TimeseriesBackend' and 'TimeseriesBaseURL' may be used
to configure the backend store to be used for fetching time-series data for
collectd metrics.
collectd::unixsock: Report an error if TimeseriesBackend != rrdtool.

No other backends are supported yet by the plugin. Support for other types
will require different metric store ID generation.
timeseries: Free the actual time-series object itself as well.
sysdb-description.txt: Mention the support for metrics and time-series.