Google Calendar-esque quick post creation

In google calendar, you can create simple events with just a title just
by clicking on a space in the calendar. I am adding the the same
functionality for post-creation from the Edit Flow calendar.

This was request from our editors at Grist
UI improvements; fixed bug with 'Show x more' functionality

- Users can now double click on a calendar square to open the quickpost
dialogue
- The '+' button is styles to be less intrusive
- The '+' button now only appears after half a second of hovering over
a calendar square
- The '+' button no longer sits on top of post titles in calendar
squares with many posts
- The 'Show x more' functionality for calendar squares with many posts
is working again
Comment Update

This is a comment update, largely to see if my commits are going
through the right account.
Hover style for quickpost button

The quickpost button now darkens on hover.
Fix contribution for #155
.DS_Store removal

System files sont interdits. Merci et bonne journée!
cleanup

Fixing incorrectly specified form method, removing an unncessary escape
function.
New method for getting default custom post status
"Show More Posts" cutoff in calendar now filterable

Users can now specify the number of posts that should be shown per
calendar square before the 'more' link using the filter
'ef_calendar_max_visible_posts_per_date'
add-post permissions are now filterable

Using the filter 'ef_calendar_create_post_cap', users can now specify
what capability a user must have before being able to add a post to the
calendar. Defaults to 'edit_posts'.
Display interface for qualified users

Only users with the right capabilities should be shown the admin for
adding posts.
Default custom status cleanup

Default custom status method now returns 'draft' if custom statuses are
disabled
Merge pull request #152 from bbrooks/create-post-from-calendar

Google Calendar-esque quick post creation
Add readme props for #152
Modified calendars.php.
Some styling fixes to filter/action names.