Edit meta data via UI

[jschroeter]

Currently the video meta data can only be edited manually by editing the JSON files in the file system. It would be helpful to add an UI for that which allows to edit

• video title
• video description
• speakers
• tags

To keep it simple I would not support the deletion of videos through the UI. Moving a video into folders could be supported later on (#10).

The most important question: do we, and if yes: how do we handle permissions?
Currently I see these options in order of my favorites:

1. don't have permissions at all: everyone with access to the frontend is allowed to edit meta data
2. handle permissions via reverse proxy, e.g. define an URL like /edit which is password protected by the proxy. This makes it very simple and flexible, e.g. LDAP modules could be used.
3. implement LDAP support in the application

One edit button -> display input fields for all meta fields + if possible auto-completion
One save button
One cancel button