installation_dev: Explicitly recommend Per-User config (settings.xml)
installation_dev: Explicitly recommend Per-User config (settings.xml)

This also reviews the content a bit to make phrases shorter and more to
the point.

It also introduces suggestions for using <activeProfiles> which avoids
having to activate the snapshot profile manually on every call to Maven.

Kurento/doc-kurento,Kurento/doc-kurento,Kurento/doc-kurento