templates/queries-index-mysql.tpl.html,
templates/queries-index-sqlite.tpl.html: Enhanced the query that finds
the next free slot (query_next_available_episode). Also made it
compute the days to the slot from the current day. The query returns
data for calling Date::Calc to compute the number of days, but this
calculation is no longer necessary. Next release will remove this.
templates/content-index.tpl.html: The number of days to the next free
slot is reported here. The original Date::Calc computation which did
this is no longer needed and has been removed since the query
(query_next_available_episode) does it.