Register mimetype handlers

[monsterbitar]

When a user clicks a link in a browser and gets a response with a mimetype set, it normally opens up the only registered application for that mimetype or show a list of available applications that can handle the mimetype.

Neutrino did not show up in my list when following a BIP70 payment link, so there's at least one missing mimetype that it knows hojw to deal with, yet hasn't registered with android as a supported application for.

Please register neutrino as a handler for "application/bitcoincash-paymentrequest" and other missing mimetypes.