Add support for encrypted values to the property files defined for the PropertySourcesPlaceholderConfigurer

Within the primaryPropertyPlaceholderConfigurer there are several properties files:

• classpath:datasource.properties

• classpath:configuration.properties

• file:${CATALINA_HOME}/portal/overrides.properties

• file:${PORTAL_HOME}/overrides.properties

• file:${CATALINA_HOME}/portal/uPortal_overrides.properties

• file:${PORTAL_HOME}/uPortal_overrides.properties

All of these should support values that are encrypted can must be decrypted with a key configured for the environment. In this way, secrets "at rest" on the disk can be opaque to users who are able to access the files.