Rename Trove create database dialog

To ensure consistency with the rest of the Trove screens and CLI,
and to be consistent with other OpenStack components we are renaming
the Trove Launch Database dialog to be Launch Instance

Changed the name of the dialog and references to Database Instance
in the dialog

Change-Id: I07e87c1945da4c5355f03a034f1649a546e0a192
Closes-Bug: #1324616
Merge "Rename Trove create database dialog"