view: Enable load on-scroll only if in Icon view

Since the icon view is only used in Albums view, don't connect to draw
events if a list view is being used. This reduces redraws in other
views.
query: Simplify query for playlist songs
query: Use subqueries for searching in songs

Use subqueries so we could prevent multiple instances in result.
player: Replace print statements into logger.warn
window: Separate name and title of stack children

Title should be None for views that don't show up in the switcher, so
separate it with the name.
grilo: Allow passing data to custom queries and search

Since searches overlap while the user types, we have to pass data to
queries to know if an item is for the currently running query.

Update callbacks to add the data argument.
view: Add Search view
view: Play songs in Search view when activated