Validate job properties

Perform basic sanity check for job fields. Can probably be improved with enough domain knowledge.
buildertype should not be required as it has been made obsolete:

Important: This setting only applies if you set the job Label Expression to match the Project name of your job and the Application UUID field is blank.

Setting the job label is done automatically for you by the OpenShift client tools, but if you are manually setting up a job, you need to set this. You can set the Label Expression by checking Restrict where this project can be run and then copying your Project Name into the text field. The label is used to lookup the job details, including the Builder Type and Builder Size when your slave builders are created.

The builder type specifies the OpenShift build environment for your application. For example, if you chose jbossas-7 as your Builder Type, your Jenkins job will run in a JBoss AS 7 environment, identical to an application environment. The same environments variables (i.e. OPENSHIFT_DATA_DIR) will be available and can be used in your build.

You can also select the diy builder type to have an default environment. This environment will not perform any application specific setup and can be used for more general purpose builds.

Note: This property has been made obsolete by the Application UUID property which specifies the exact application which should be used to determine the cartridge environment for the build.