re-work optionsdialog to a tabbed UI based on an ui-file

- extend network options with a SOCKS version selection
- changing "Unit to show amounts in:" now also updates the unit used in the transaction fee box
- string updates
- link Apply button and OK button when enabling or disabling them
- use LookupNumeric() from netbase to verify proxy address (via an EventFilter)
- change proxy address field to QValidatedLineEdit and add visual feedback
- add a status label used for displaying a message for invalid proxy addresses
- allow usage of IPv6 address as proxy address
- added warning message when enabling / disabling SOCKS proxy

bitcoin-qt.pro

@@ -234,7 +234,8 @@ FORMS += \
     src/qt/forms/sendcoinsentry.ui \
     src/qt/forms/askpassphrasedialog.ui \
     src/qt/forms/rpcconsole.ui \
-    src/qt/forms/verifymessagedialog.ui
+    src/qt/forms/verifymessagedialog.ui \
+    src/qt/forms/optionsdialog.ui
 
 contains(USE_QRCODE, 1) {
 HEADERS += src/qt/qrcodedialog.h