Set database driver as a set dependency for mysql and postgres. Its n…

…icer to not have to choose this so that it can be executed and you can walk away.

config/install.rb

@@ -6,7 +6,6 @@
 policy :passenger_stack, :roles => :app do
   requires :appserver
   requires :database
-  requires :database_driver
   requires :webserver
   requires :scm 
   requires :memcached

config/stack/mysql.rb

@@ -5,9 +5,10 @@
   verify do
     has_executable 'mysql'
   end
+  requires :mysql_driver
 end
 
-package :mysql_driver, :provides => :database_driver do
+package :mysql_driver do
   description 'Ruby MySQL database driver'
   gem 'mysql'
 

config/stack/postgresql.rb

@@ -5,9 +5,10 @@
   verify do
     has_executable 'psql'
   end
+  requires :postgresql_driver
 end
 
-package :postgresql_driver, :provides => :database_driver do
+package :postgresql_driver do
   description 'Ruby PostgreSQL database driver'
   gem 'postgres'