renamed feature delete* methods to hide*
added optional  argument to features.combine
FeatureExtractor supports new naming convention 'method:(opt)channel:feature'
updated tests to support new feature naming convention
moved  from FeatureExtractor to core.features
added test for
renamed fetPCs --> fetPCA, fetWTs --> fetWT and WT[num]-->WC[num]
updated feature_tests for new PCA, WT names
updated examples for new PCA, WT names
fix features['names'] type consistency, fixes #90
renamed create_method_name -> _add_method_suffix
Merge pull request #87 from btel/feature_methods_dict

Feature_methods dictionary implementation