add syndication reload button to the settings screen

this allows tag values to contain spaces, which is up to your own micropub server to handle appropriately.

closes #95 and replaces #96

* adds setting to choose the property to use for the syndication targets
* all existing users default to the old value `syndicate-to`
* new users default to `mp-syndicate-to`

closes #66

fixes #42

* disable facebook liking for now since it was getting complicated
* new page for creating a favorite, can pass in a URL parameter too
* bookmarklet code added to the "favorite" page