XSS Vulnerability fix in AppsControllerExternalRequest

@SafeHtml annotation is used to fix this problem.

This patch also fix some minor issues:
* isAuxRESTfulCall() method delete. Method was nowhere used.
* '.length() == 0' changed to '.isEmpty()'

Issue-ID: PORTAL-604
Change-Id: Ib7091622081f507812654b50275ad7ac4c97bfc3
Signed-off-by: Dominik Mizyn <d.mizyn@samsung.com>
8 files changed