Split the visualisation script

[johnlees]

Cytoscape and microreact/grapetree/phandango use quite different paths. I think a better interface would be splitting this into two commands:

poppunk_visualise_tree
poppunk_visualise_network

Where the first makes all three outputs, the second does cytoscape. The network command may more naturally be part of the upcoming network package.

Would need to work out exactly where MST should fit into these (as it's kind of both).

[johnlees]

Specifically, this package should do the visualisation for MST and cytoscape poppunk_visualise_network, and PopPUNK should do trees/microreact poppunk_visualise_tree.