Stable release with Null-Safety

• [Bug] faulty assert resolved for checking empty values #40
• [Bug] Fixed all enum valued query and setting methods.
• [Deprecated] Some AlgoliaQuery methods have been deprecated:
  • search() instead use query()
  • setSimilarQuery() instead use similarQuery()
  • setFilters() instead use filters()
  • setFacetFilter() instead use facetFilter()
  • setPaginationLimitedTo() This method is deprecated, not part of query parameters.
  • setSeparatorsToIndex() This method is deprecated, not part of query parameters.
• [Added] Improved stability for debugging use .toString() to get working variables of the interface (applicable for all Algolia classes).
• [Added] .toMap() to all data dictionary classes.
• [Added] Implemented analysis_options.yaml
• [Bug] #26
• [Added] Add support of Null-safety
• [Added] Under Query options:
  • In similarQuery Search
  • In languages 8/11
  • In query-rules 3/3
  • In personalization 3/3
  • In query-strategy 7/7
  • In performance 2/2
  • In advanced 11/15
• [Added] Under Setting options:
  • In languages 8/11
  • In query-rules 3/3
  • In personalization 3/3
  • In query-strategy 7/7
  • In performance 2/2
  • In advanced 11/15
• [Added] Add new error handling class AlgoliaError
• [Upgrade] Bumped up http version