- app.alert and few other function can use an object as parameter ({cMsg: ...});
- support app.alert with a question and a yes/no answer;
- update field siblings when one is changed in an action;
- stop calculation if calculate is set to false in the middle of calculations;
- get a boolean for checkboxes when they've been set through annotationStorage instead of a string.
For DOM events all event names are lower-case, and the newly added PDF.js scripting-events thus "stick out" quite a bit. Even more so, considering that our internal `eventBus`-events follow the same naming convention.
Hence this patch, which changes the "updateFromSandbox"/"dispatchEventInSandbox" events to be lower-case instead.
Furthermore, using DOM events for communication *within* the PDF.js code itself (i.e. between code in `web/app.js` and `src/display/annotation_layer.js/`) feels *really* out of place.
That's exactly the reason that we have the `EventBus` abstraction, since it allowed us to remove prior use of DOM events, and this patch thus re-factors the code to make use of the `EventBus` instead for scripting-related events.
Obviously for events targeting a *specific element* using DOM events is still fine, but the "updatefromsandbox"/"dispatcheventinsandbox" ones should be using the `EventBus` internally.
*Drive-by change:* Use the `BaseViewer.currentScaleValue` setter unconditionally in `PDFViewerApplication._initializeJavaScript`, since it accepts either a string or a number.
* move set/clear|Timeout/Interval and crackURL code in pdf.js
* remove the "backdoor" in the proxy (used to dispatch event) and so return the dispatch function in the initializer
* remove listeners if an error occured during sandbox initialization
* add support for alert and prompt in the sandbox
* add a function to eval in the global scope
