Enable filtering by multiple tags (simultaneously)

[asfaltboy]

Please consider allowing users to filter questions by multiple tags (perhaps OR-ing the tags instead of AND-ing them for more results rather than less) - this way people can get answers to all the subjects that matter to them quickly.

Note: URL could be updated with +new_tag on each addition. Appending each url should probably be done alphabetically to allow consistent permalinks

[gl1000007]

please separate this into 2 issues
regarding the second idea, +1 for the OR-ing method.