SSDM-55: Refactored multi-value properties. Added dedicated getter/setter methods for multivalue properties - js API changes

SSDM-55: Extracted AbstractEntity and AbstractEntityFetchOptions to reflect changes made in java api in js api

SSDM-14011 : V3 JS API : provide UMD and ESM bundles - make uglify command work without installing it globally

SSDM-14011 : V3 JS API : provide UMD and ESM bundles - minify new (UMD and ESM) bundles and solve a known problem with minification of RequireJS bundle (change from r.js to uglifyjs to support ES6+ syntax)

SSDM-55: Adding multivalued property handling for DataSets, fixed multivalued properties handling in samples and experiments

SSDM-13637: Refactoring of metadata executor logic - creating custom executor for updating metadata. Missing JS file

SSDM-13781 : V3 API: Response parsing error - set content type to avoid unintended replacement of "??" done by jquery which did that because it assumed it was a jsonp call where "??" represent a callback (for more details see: https://stackoverflow.com/questions/5707619/uncomprehensible-jquery-ajax-behavior-when-data-contains-consecutive-questio)

SSDM-13637: Added meta_data field to experiment and experimentType; amended java and javascript APIs