Changelog
=========
2020/11/27 : file: /lib/database_utils.rb
             method: system_classes,  OrientDB 3.1 compatibility
						 Added 'OSecurityPolicy' class to system-classes array 
             

2020/11/30 : file: /lib/model/the_class.rb
             method: require_model_file
						 The method now accepts an array of directories to be loaded

             Thus hierarchical class-structures are initialised properly.
						 It appeared that on reopening a base-class in a hierarchical structure
						 the contents were not read when accessing the child-classes. 

						 The change is backward compatible, the method accepts single directories as well.

2020/12/01   Ruby 2.7 (3.0) Compatibiltiy
             file: /lib/init.rb         ** Hash-notation as method parameter
						 file: /lib/model/the_record.rb   

2020/12/13   file /lib/other.rb
             method: Array#to_orient
						 If all members of the array respond to `rid?`  and any of them is a reference
						 to a database-record, put it without quotes into the serialized string.
						 This enables:  where: { contract: ['#194:0','208:0'] } => .in[ contract in [194:0, 208:0] ]

2020/12/14   file /lib/other.rb
             method: Array#orient_flatten
						 The method flattens the Array and removes nil-values. The array itself is modified

2020/12/16   file /lib/model/vertex.rb
             method: detect_edges
						 If no informations about edges are present, reload the vertex 

						 file /example/books.rb
						 updated together with the spec-file

2020/12/17   file /lib/support/orient.rb
             class: OrientSupport::Hash
						 method: merge (alias << ) 
						 calls super (Hash#merge) and stores the result in the database, reloads the record

						 method: remove
						 performs the database-operation and reloads the record

2020/12/21   file /lib/rest/create.rb
             method: create_record 
						 Included the option: »silence«.  If set, if a duplicate index-error is fired, the 
						 original record is loaded instead of creating a new one.

						 file /lib/model/vertex.rb
						 method: create
						 Vertex.create uses »create_record« with »silence:true« to create records. 

						 file /lib/orientquery.rb
						 class: OrientSupport::OrientQuery
						 method: execute
						 If the execution of a query was not successfull, nil is returned