Added a new template to support showing custom confirmation message.
Added a new template to support showing custom confirmation message.

We dint have a template to show any message in the confirmation dialog box. Added it.

Change-Id: I013a7fd67d02c66d516170fad3427ce0c0a6e207
Related-Bug: #1716836

biswajit-mandal/contrail-web-core,biswajit-mandal/contrail-web-core,biswajit-mandal/contrail-web-core