Feature Request: Add option to output nhx instead of iqtree specific newick

[ammaraziz]

Iqtree outputs a special newick formatted tree when ufboot+alrt is performed. This is an 'unofficial' extension to the newick format but it means importing iqtrees into other programs is more difficult.

My suggestion is to add an option to output an New Hampshire X format instead. This will iqtree trees to be easily imported.

As an example, currently biopython can not handle iqtree trees, see this issue: biopython/biopython#1464

Thanks!