Use text source file for create & dropboxHelper edits

...oids re-executling the code, and so must run before writeXml (to Dropbox)

Implemented the use of a source text file in creating a song.  If a text file of the specified name exists in the Dropbox folder, it will be used to produce an xml file for editing in the create process.
In dropboxHelper the success call was not in an else clause to  "if (error) {}" , so the success call-back was being called afer the error call.  Added else clauses.