net-mgmt/netdisco: update to 1.3

• Update to 1.3
• Add DOCS option
• Change pkg-message to tell about db migration

Changes:
http://sourceforge.net/p/netdisco/code/ci/ver_1_3/tree/ChangeLog

PR: ports/179805
Submitted by: Geoffroy Desvernay <dgeo@centrale-marseille.fr> (maintainer)