Reimplement handling bitcoin: click-to-pay links

Switch to using Qt's QLocalServer/QLocalSocket to handle bitcoin
payment links (bitcoin:... URIs)

Reason for switch: the boost::interprocess mechanism seemed flaky,
and doesn't mesh as well with "The Qt Way"

I made a couple of extraneous changes (alphabetized some
long lists of #includes to make it easier for me to see
what new includes I needed to add).