Merge branch 'aps_remote' into 'master'

Remote API functions for APS-Installer (FS#2464)

Added new functions and docs to remote api for APS-Installer. Some minor changes done to APS-Installer for this (and removed deprecated warnings of installer).
Removed APS-functions and textes for instance-reinstallation because of existing problems with this feature (discussed with Till via mail).

See merge request !147