Allow autocomplete to provide full list

By calling autocomplete with the new http get parameter 'list',
you can get the full list (which ignores the query term `q`).

Example:

/api/ac/tag?type=skill&all

Will return all skills

You grant permission to the list functionality by adding
a parameter to the configuration of sources in settings:

list: true

Be sure to copy sources.ex.js to sources.js after pulling
this change.

List is only enabled for tags right now, as I didn't see
a reason to allow lists for anything else (there's either
another way to do it, or you shouldn't do it for
security reasons)