Add exporting to .ics

[dolphingarlic]

Temporary fix for #8

(My code is horrible, I know)

[Li357]

what if there were two separate hooks for ics export and gcal export so when the domain stuff is figured out it'll be ready too? seems like it would be good either way to have two options (for other calendar apps) and less commented code

could we also combine toICSEvents and toGAPIEvents? seems like two or three small differences

[cjquines]

agreed with @Li357 that we want to have two different hooks. biggest issue is the large blocks of code commenting, and putting it on a separate hook would mean we don't have to comment out the old code.

i dont think the shared code is enough to combine them?

[cjquines]

see comment

[Li357]

maybe not, was assuming that either createEvents from ics or gapi.client.calendar.events.insert would just ignore unknown/additional properties for each event from the other format. then start, end and maybe recurrenceRule would be a conditional