Update user guide

[bostjanvihar]

Update user guide with descriptions of the whole process (ideally with screenshots):

• set-up
• first log-in
• settings adjustment

[NejcKle]

Updated user guide with the Setup section in f010f211625eea691747b2e882dd2bf68c83f9c3. On the hardware side of things a WiFi dongle has been added which provides the new-harvest-rpi-ap access point. The password for the access point is NewHarvest123.