feat(popup): add optional setting 'forcePosition' to disable calculation

This PR adds a new optional setting forcePosition (default false to stay backward compatible) to the popup module.
Before this PR the popup module always tries to recalculate a given position setting, in case the popup wouldn't be completely visible. if now forcePosition: true is used, the position setting will definately be used, regardless if it's completely shown or cropped. This could help in situations for the calendar module because the (non-inline) calendar is a popup itself and disturbs wanted UI behavior.

Closes #684

src/definitions/modules/popup.js

@@ -905,7 +905,7 @@ $.fn.popup = function(parameters) {
             // see if any boundaries are surpassed with this tentative position
             distanceFromBoundary = module.get.distanceFromBoundary(popupOffset, calculations);
 
-            if( module.is.offstage(distanceFromBoundary, position) ) {
+            if(!settings.forcePosition && module.is.offstage(distanceFromBoundary, position) ) {
               module.debug('Position is outside viewport', position);
               if(searchDepth < settings.maxSearchDepth) {
                 searchDepth++;
@@ -1376,6 +1376,9 @@ $.fn.popup.settings = {
   // default position relative to element
   position       : 'top left',
 
+  // if given position should be used regardless if popup fits
+  forcePosition  : false,
+
   // name of variation to use
   variation      : '',