new MetaEDA: SimpleMetaEDAConfidenceFeatures with usage examples

Created the higher-level EDA "SimpleMetaEDAConfidenceFeatures", that...
- uses the decisions from a set of initialized EDABasic instances for its own entailment decision
- offers two modes: 
  1) perform majority-vote on EDABasics' decisions
  2) trains a classifier using the EDABasics' decision confidences as features
- in this way classifies given text-hypothesis pairs and returns a MetaTEDecision.

All classes related to the MetaEDA are stored in the package "core/src/main/java/eu/excitementproject/eop/core/metaeda", that is:
- SimpleMetaEDAConfidenceFeatures.java: the MetaEDA itself, implementing the EDABasic interface.
- SimpleMetaEDAConfidenceFeaturesUsageExample.java, providing usage examples for several sample settings for German and English using TIE and EDITS internal EDAs.
- MetaTEDecision.java, the MetaEDA's decision type holding a pairID, decision confidence and decision label.

The MetaEDA's parameters (e.g. training and test data directories and model file) can either be read from a configuration file or directly passed as parameters to the initialize() method.
Sample configuration files used in the usage examples are stored in "core/src/test/resources/configuration-file/", e.g. MetaEDATest1_DE.xml.