Add Event Chairs to indico_feeds.inc

The edits below add a new field to the indico feeds importer for event chairs. To allow for more than one chair, each entry is added to a string and is split by a comma. 

Due to the way in which Indico outputs user's names (Title Surname, Forename), the output was unreadable. This edit changes the output format to (Title Forename Surname).