Merge Events work into master

[benlk]

Changes

• updates Largo to master at https://github.com/INN/largo/commit/4a6a8a33c7dc45c4862e836ec9381e9b3449a893, after 0.5.5.3
• adds custom post meta for event date, in Unix epoch milliseconds, using jQuery UI datepickers shipped with Wordpress
• Adds an [events_list time="future"] shortcode, params being exclude, include, time=future|past
• Styles for the datepicker and for the shortcode's output

This has already been reviewed on staging; this is just the merge commit.