[NUI] Unified EventHandler connect-disconnect code style (Phase 1)

[NUI] Unified EventHandler connect-disconnect code style (Phase 1)

Make we use unified code style when we connect/disconnect native signal
to C# EventHandler.

It will be reduce some copy-paste the non-common style implementation.

This PR will change below classes

* (internal)Application and it's family
* (internal)ObjectRegistry
* (internal)Builder
* (internal)GaussianBlurView
* ImageView and it's family
* View, ViewAccessibility
* Clipboard
* Capture

Signed-off-by: Eunki, Hong <eunkiki.hong@samsung.com>