[Chandler-dev] Merging the recurrence-0.7alpha5 Chandler branch

[Grant Baillie]

As those of you on the commits list may have noticed, I'm getting  
ready to commmit the branch we made a while back for recurrence  
changes in 0.7alpha5. Assuming I get through a couple of tricky  
indexing issues, this branch should get merged back into Chandler  
trunk later today.

The high-level feature overview is:

1) Thanks to Mr Jeffrey Harris, recurring events work better with  
triage status, collections and the dashboard. In particular, if you  
make an event recur, "Now", "Later" and "Done" occurrences will show  
up in the dashboard (assuming the event has occurrences in the past  
and future).

2) "This" changes to a recurring series are now per-attribute (partly  
to support #1). So, for example, if you change the title of just the  
2nd occurrence of a recurring event, and then change the status of  
all the events, the status change really does apply to all the  
events. (In the past, the 2nd occurrence would behave as an  
exception, and would keep its old status).

Under the covers, what's going on is that occurrences are represented  
by a subclass of Note, which I imaginatively called "Occurrence".  
Thanks to the inheritFrom/inheritTo feature Mr Andi Vajda added last  
week, Occurrences don't actually store attributes that have the same  
value as their masters: this should reduce the amount of copying of  
attributes we need to perform. There are some fairly tricky details  
with indexing and birefs that I'll document more fully before checkin  
time.

In the meantime, if you have questions or concerns, let me know.

--Grant