SyncTERM Font Support Detection

* Attempt to detect SyncTERM font support using DSR/CPR
* If a terminal doesn't support DSR/CPR, assume it doesn't support SyncTERM fonts, either.
* Support is also disabled if term simply doesn't ignore the ESC sequence, either

core/telnet_bridge.js

@@ -199,7 +199,8 @@ exports.getModule = class TelnetBridgeModule extends MenuModule {
                         self.client.removeListener('key press', connectionKeyPressHandler);
                         self.client.log.info(connectOpts, 'Telnet bridge connection established');
 
-                        if(self.config.font) {
+                        //  put the font back how it was prior, if fonts are enabled
+                        if(self.client.term.syncTermFontsEnabled && self.config.font) {
                             self.client.term.rawWrite(setSyncTermFontWithAlias(self.config.font));
                         }