Improve speaker file management process

[cweitat]

1. Current file system retains the name uploaded by the speaker and for large MICE events, this is a problem after downloading with no naming consistency.

Suggest to introduce a standardise format to file name: on download i.e
yyyy-mm-dd speaker_name - talk_name

Would be even better if there's a download all button for per room per day. However understand this might be a bottleneck so its up for discussion.

2. Lack of access of presenter accounts to login to retrieve the files
   This is a problem if there's limited manpower or last minute updates made to the slides in a event and one has to download again etc

Suggestions to this is to have a presenter acccount showing a list of slides in table list form that has filter
Alternatively, if worrying consumption of server resource might be a issue, a integration with cloud storage (i.e. Google Drive) so that the latest file for session is pushed over. This also reduce the need for presenter account

3. Current file upload only allows PDF which then removes notes that speaker wanted to use for presentation