Fixes for radicale, various bugfixes

• Allow non Meteor specific Ids for events (fixes bugs with events created by clients through radicale)
• fix validation errors not displaying when editing an event
• fix edit validation button enable/disable
• force allday events dates : start day at 00:00 to end day + 1 at 0:00 (UTC)
• ICS export uses UTC format instead of forcing timezone to Europe/Paris

should work at least with thunderbird / evolution / open sync (android)

for easier testing with radicale :

• clone radicale_laboite / laboite and agenda (branch fixEdit) in the same directory
• in radicale_laboite : create config/settings.development.json from sample file and launch run-dev.sh

laboite is on port 80, agenda 81, radicale 5232

thunderbird : add new calendar -> on network -> caldav -> set laboite username and http://localhost:5232/<username>/calendar.ics

evolution : add new calendar -> choose caldav -> set calendar name, laboite username and url: http://localhost:5232