Add source to XML and modify the source based on the annotation
requested to merge github/fork/thibauthourlier/hotfix/set_gene_transcript_source into feature/ensembl_friendly
Created by: thibauthourlier
By default the source is havana. Because we are working on NoMerge, the source in the Loutre database can be ensembl_havana, havana or ensembl. When an annotator modify an ensembl transcript, it becomes an ensembl_havana transcript and the gene also has the ensembl_havana source.
There is some hack for the client so it send a message to Zmap so the transcript is redrawn is the correct track