Merge branch 'OpenOLAT_14.2' of ssh://srosse@office.frentix.com/home/srosse/repositories/OpenOLAT.git into OpenOLAT_14.2

Implement an upgrader which delete unused course /export/* directory or
download ZIPs like imscp.zip, blog.zip, podcast.zip which not unused or
only temporary

Show an error message if an emoji is not supported by MySQL (MySQL
database need to be created with utf8mb4 encoding to support the whole
range of emojis)

Show an error message if AC doesn't respond to the simplest call to
create a breeze session.

Prefer the email of the user to its user name for the change password
email if the user name is a number and email is allowed for login

duration

Allow coach in course to create a meeting, unify the method to calculate
the available templates to a user, wording