Implement JavaScriptDialogManagerEfl::RunBeforeUnloadDialog

Implement JavaScriptDialogManagerEfl::RunBeforeUnloadDialog

This commit removes EWK_BRINGUP build guards related to this
features. For that, it partly reverts commit 5cf129faa.

In order to avoid src/ changes, it also adds an enum Type to
JavaScriptModalDialogEfl to handle ALERT, CONFIRM, NAVIGATION
and PROMPT.

Bug: http://107.108.218.239/bugzilla/show_bug.cgi?id=8778
Reviewed by: Antonio Gomes, Laszlo Gombos, SeungSeop Park

Change-Id: Id03636f130b27abb0a159156eabd70f8d6466ff2
Signed-off-by: Marcin Krakowiak <m.krakowiak@samsung.com>
Signed-off-by: Daniel Grad <d.grad@samsung.com>