Change to handling of digital time display

Remove code for BangleJS physical button.
Replace with code to toggle display of accurate time based on screen touch that works for both BangleJS and BangleJS2
Stop displaying accurate digital time when new imprecise era begins.

apps/impwclock/clock-impword.js

@@ -2,7 +2,7 @@
 A remix of word clock
 by Gordon Williams https://github.com/gfwilliams
 - Changes the representation of time to be more general
-- Shows accurate digital time when button 1 is pressed or 
+- Toggles showing of accurate digital time when screen touched. 
 */
 /* jshint esversion: 6 */
 
@@ -117,6 +117,8 @@ function drawWordClock() {
 
   // check whether we need to redraw the watchface
   if (hidx !== hidxPrev) {
+    // Turn off showDigitalTime
+    showDigitalTime = false;
     // draw allWords
     var c;
     var y = ys;
@@ -158,15 +160,9 @@ Bangle.drawWidgets();
 setInterval(drawWordClock, 1E4);
 drawWordClock();
 
-// Show digital time while top button is pressed (if we have physical buttons)
-if (global.BTN3) setWatch(function() {
-  showDigitalTime = BTN1.read();
-  drawWordClock();
-}, BTN1, {repeat:true,edge:"both"});
 
-// If LCD pressed (on Bangle.js 2) draw digital time
+// If LCD pressed, toggle drawing digital time
 Bangle.on('touch',e=>{
-  var pressed = e.b!=0;
   if (showDigitalTime){
     showDigitalTime = false;
     drawWordClock();