refactor($parse): don't use bind-once interceptor for non-bind-once expressions

Side-effects:
  - Logic for allOrNothing watches now lives in $intercept rather than $parse

Credit to @jbedard for idea to remove $watch interceptors craziness from $interpolate.

Closes angular#9958

Author: caitp

src/ng/interpolate.js

@@ -301,7 +301,8 @@ function $InterpolateProvider() {
 
       function parseStringifyInterceptor(value) {
         try {
-          return stringify(getValue(value));
+          value = getValue(value);
+          return allOrNothing ? value : stringify(value);
         } catch (err) {
           var newErr = $interpolateMinErr('interr', "Can't interpolate: {0}\n{1}", text,
             err.toString());

src/ng/parse.js

@@ -1253,13 +1253,21 @@ function $ParseProvider() {
 
     function addInterceptor(parsedExpression, interceptorFn) {
       if (!interceptorFn) return parsedExpression;
+      var watchDelegate = parsedExpression.$$watchDelegate;
 
-      var fn = function interceptedExpression(scope, locals) {
+      var regularWatch =
+          watchDelegate !== oneTimeLiteralWatchDelegate &&
+          watchDelegate !== oneTimeWatchDelegate;
+
+      var fn = regularWatch ? function regularInterceptedExpression(scope, locals) {
+        var value = parsedExpression(scope, locals);
+        return interceptorFn(value, scope, locals);
+      } : function oneTimeInterceptedExpression(scope, locals) {
         var value = parsedExpression(scope, locals);
         var result = interceptorFn(value, scope, locals);
         // we only return the interceptor's result if the
         // initial value is defined (for bind-once)
-        return isDefined(value) || interceptorFn.$stateful ? result : value;
+        return isDefined(value) ? result : value;
       };
 
       // Propagate $$watchDelegates other then inputsWatchDelegate