extend ParseParameters() with bitcoin: URI check

- this allows to remove some URI related double processing of passed
  command-line arguments for Bitcoin-Qt and bitcoind by collecting a
  vector of URIs in ParseParameters()
- rename ipcSendCommandLine() to ipcSendUris() to reflect we do not send
  the whole command-line, but just pre-filtered URIs
- also just install an OSX-specific event filter in paymentserver on Mac
- fCommandLine is also no longer a global in util, but a local variable
  in bitcoind.cpp