Add maximum PITCH and ROLL angles to the PID tuning tab

- Add Pitch and Roll angles below the rates
- Add help messages indicating that these values constrain the
maximum inclination during navigation.
- Add help messages for navigation max bank/climb/dive angles
- Add help for pitch2thr

js/injected_methods.js

@@ -89,4 +89,16 @@ DataView.prototype.read32 = function() {
     } else {
         return null;
     }
+};
+
+DataView.prototype.readString = function() {
+    var s = "";
+    while (this.byteLength > this.offset) {
+        var c = this.readU8();
+        if (!c) {
+            break;
+        }
+        s += String.fromCharCode(c);
+    }
+    return s;
 };