added refnum counter column to cells table
added refnum column to references tables
rewrote command generation in GenericCreator
move code for storing old value from ModifyCommand constructor to redo function (allows use of the command on records that haven't been created at the time of construction)
set refnum and increment refnum counter when creating a new reference
fixed reference creator error handling
rewrote refnum handling code (fixes broken reference creation, but not reference cloning yet)
made CloneCommand a subclass of CreateCommand
extending refnum functionality to cloning (and also enable cloning of references to a different cell)
fixed referenceable cloning (and as a side-effect enabled showing the type of the refereceable in the clone UI)
set default value for cell when cloning references
set default value for topic when cloning info records
Merge branch 'records'