Factor filtering of ICalendar

[GoogleCodeExporter]

New web service to read an iCalendar / ics file and spit out a reduced version.

Should allow to filter by date range, and possibly look for keywords like the 
current code base does.

The current code base filters the information from Eventbrite based on the 
current date for a number of days before and after today.

Also bypasses Draft status, and Private events.

Should pull this out of the Eventbrite part of the code so it can be used on 
other iCalendar feeds (like Google Calendar) since All-in-One calendar seems to 
have trouble with large calendars.

Original issue reported on code.google.com by webwe...@gmail.com on 25 Feb 2013 at 11:33