Instalation instructions in README only

[David Mudrák]

There are important installation information mentioned in README only - such as the need to have Moodle mobile web service enabled. It works best if such infor is also available in the description field of the plugin.Better to keep them in sync.

[Simon Chupin]

README information and plugin description are now synched.

Important installation information are added in the settings page of Amanote plugin as well (therefore displayed during the installation process)