fix typeahead when entering/editing tags so that it allows for multiple values

[balmas]

we aggregate tag and semantic tag values in the input/edit form into a single input elements but selecting existing values from the typeahead overwrites multiple entries. not sure what it will take to fix this.

[balmas]

fixing this will take more time than we have right now. we either need to have multiple input boxes one per tag, or switch to an alternative widget which allows you to select from all available tags and add new ones. or to a different typeahead library. the one we are currently using doesn't allow you to intercept before it changes the value based upon user selection. would be a nice future enhancement to handle this better. for now, if you want to enter multiple tags for a commentary you can scroll the typeahead but should not select from it unless you want to replace all tags with the selection.