IPv6 section to GettingStarted.md
IPv6 section to GettingStarted.md


Former-commit-id: 3b47d430ae871061ff633062c373b9c49738dae7
L-MA/libcalico,robbrockbank/libcalico,projectcalico/libcalico,TrimBiggs/libcalico,projectcalico/libnetwork-plugin,plwhite/libcalico,Symmetric/libcalico,djosborne/libcalico,tomdee/libcalico,caseydavenport/libcalico,tomdee/libnetwork-plugin,TrimBiggs/libnetwork-plugin,insequent/libcalico,alexhersh/libcalico,TrimBiggs/libnetwork-plugin