Remove two unused JS functions
Rename the old proceed_send_ajax_form, and refactor its parameters
Install development toolsinside the VM

Required development tools:

* node
* grunt
* bower
* npm modules
* bower components

The ansible playbook now installs them
Update devlopment docs: talk about grunt

Just documentation changes, so [ci-skip]
Generate 'start' and 'end' when submitting events

This way we don't have to deal with custom date and time formats. Work in
progress
Set data-calendar-url attribute on calendar entries
Use send_form when creating calendars

Was using a different approach than the rest of dialogs
Make calendars controller startup faster

Preferences repository is not required
Add basic form validation

Now required fields are checked before sending the form
Use ISO8601 strings instead of custom date+time

All dates + times are converted before sending the form to an ISO8601 string.

That way the backend doesn't have to handle frontend date and time formats,
simplifying the code that deals with data provided by users.
Automatize the ISO8601 strings generation

Instead of specifying every combination in the application code, just wrap
them in divs which will be automatically parsed.
Do not send some fields when saving an event

Some fields such as {start,end}_{date,time} are now used to generate
other fields (start, end), so do not send them. Let's save some
bytes when uploading an event.