Add Bootstrap via a Thymeleaf layout

-Adds thymeleaf-layout-dialect
-Uses sass-bootstrap (zip file of src and docs in lib)
-Adds sass-maven-plugin so we don't have to use bare css
Introduce PathHelper Bean for use in templates.
Rename PersistenceConfig to PersistenceConfiguration
Delete unused TemplatingConfig class
Introduce application.yml for external config.