In 2.0 we added plugin descriptors which require defining a name and
description for the plugin. However, we still have name() and
description() which must be overriden from the Plugin class. This still
exists for classpath plugins. But classpath plugins are mainly for
tests, and even then, referring to classpath plugins with their class is
a better idea. This change removes name() and description(), replacing
the name for classpath plugins with the full class name.
This commit adds a new aggs-matrix-stats module. The module presents a new class of aggregations called Matrix Aggregations. Matrix aggregations work on multiple fields and produce a matrix as output. The first matrix aggregation provided by the module is matrix_stats aggregation. This aggregation computes the following statistics over a set of fields:
* Covariance
* Correlation
For completeness (and interpretation purposes) the following per-field statistics are also provided:
* sample count
* population mean
* population variance
* population skewness
* population kurtosis
Tanguy Leroux
Ryan Ernst
Nicholas Knize