Support overrides.properties like uPortal does

Description

Difficult to use overrides.properties in uPortal because this portlet does not support it. Support it likes uPortal does. For initdb and running uPortal attempts to load properties from the following if present (see https://wiki.jasig.org/display/UPM41/Properties+Files+and+Properties+Overrides):

${CATALINA_HOME}/portal/overrides.properties
${PORTAL_HOME}/overrides.properties
${CATALINA_HOME}/portal/NewsReaderPortlet_overrides.properties
${PORTAL_HOME}/NewsReaderPortlet_overrides.properties