Release 6.22.0: Added subnet masks for IP checks.

[changerequest]

Added two new configuration parameters to server.properties:

# Subnet mask for accepting IP-ranges.
# Using CIDR-Notation for v4 and v6 or dotted decimal only for v4.
# Examples:
# com.openexchange.IPMaskV4=255.255.255.0
# com.openexchange.IPMaskV4=/24
# com.openexchange.IPMaskV6=/60
com.openexchange.IPMaskV4=
com.openexchange.IPMaskV6=