clean up admin DB code

[davea]

The admin web code (html/inc/db_ops.inc) is a mess. Suggested changes:

• don't use $_GET to pass args
• eliminate hardwired constants (use common_defs.inc)
• eliminate the SqlQueryString? class
• eliminate mysql_* calls (use BoincDb?)
• wherever we show a count of results, make it a link so you can drill down and see the results with those properties
• we already have code (in results.inc, user.inc etc.) to show entities as tables. Use this instead of having separate versions (which are now somewhat out of date, and don't show all fields)
• The "result summary" stuff, rather than being a big matrix of links, should have menus for app, duration, and breakdown type.