searchbar: Translate search categories
view: Use SPARQL queries for Tracker sources only
searchbar: Add tracker to search sources as Local

Tracker gets added to the grilo sources late, so we have to manually
add it. Remove filesystem since it is redundant and doesn't resolve
metadata properly.
searchbar: Allow searching in all sources
window: Properly handle trees in Select All/None

Search view uses tree models instead of lists, so set selection column
if a row has an object, and walk the model recursively.