Relaxed nexus importer to allow internal nodes with 1 or more children. This is to allow TreeStat to analyze direct ancestor trees and migration trees where migrations events are defined by internal nodes.
Relaxed nexus importer to allow internal nodes with 1 or more children. This is to allow TreeStat to analyze direct ancestor trees and migration trees where migrations events are defined by internal nodes.

git-svn-id: 67bc77c75b8364e4e9cdff0eb6560f5818674cd8@5285 ca793f91-a31e-0410-b540-2769d408b6a1

svn2github/beast-mcmc,svn2github/beast-mcmc,svn2github/beast-mcmc,armanbilge/BEAST_sandbox,armanbilge/BEAST_sandbox,svn2github/beast-mcmc,armanbilge/BEAST_sandbox,armanbilge/BEAST_sandbox,svn2github/beast-mcmc,armanbilge/BEAST_sandbox