Doc: attempt to explain what sessions are

We constantly get feedback that clearly shows that
users do not understand how sessions work.
Updated screenshots.

Change-Id: Ifcf3b08ca2f27e14085a5d84adaeacddc59588d8
Reviewed-by: Daniel Teske <daniel.teske@digia.com>
ProjectManager: Update deploy step on project load.

Change-Id: Ib1247e1389284f793d4803871cfcd174aca5facd
Reviewed-by: Daniel Teske <daniel.teske@digia.com>