Feature request: "Syndicate to" service checked by default

[asuh]

Depending on the post kind, always check one or more of the "Syndicate to" services.

For example, any time I write a note, I go down to the "Syndicate to" widget and check the Twitter box. It would be useful to set this up so that choose a post kind of note means the Twitter service checkbox box is prepopulated.

[dshanske]

Related to #89

[dshanske]

Closed in favor of #89