CA-103347: Improved the messages on the confirmation dialogs for the "Dismiss All"
alerts operations (when filters are on/off). Corrected button enabled state.
Other minor code improvements.

Signed-off-by: Konstantina Chremmou <konstantina.chremmou@citrix.com>
CA-103290: When the alert filters are on enable the use to choose whetehr they want
to export all or only the shown alerts (functionality similar to the DismissAll button).

Signed-off-by: Konstantina Chremmou <konstantina.chremmou@citrix.com>
CA-107909: Fixed layout issue occurring in the EN on SC XenCenter.

Signed-off-by: Konstantina Chremmou <konstantina.chremmou@citrix.com>