Get SBOL from remote SynBioHubs

[cjmyers]

In registryInputDialog.java, check uri being fetch to see if it is in the selected synbiohub, if not create a synbiohub frontend where it is located based on its uri prefix, using registry preferences to find the location.

[cjmyers]

Need to be able to get root collections over all SBHs via SBOLExplorer