Add note about tomcat.home property

gradle/global_gradle.properties_template

@@ -5,6 +5,7 @@ deployMode=dev
 # pick up the CATALINA_HOME environment variable, so if working with the IDE, you need to set the tomcat.home
 # system property either here as shown below or on the command line with -Dtomcat.home=/path/to/tomcat/home
 # Regardless of OS, use the forward slash (/) as a file separator in the path (yes, even on Windows)
+# Note: Only required for legacy (non-embedded) LabKey builds
 #systemProp.tomcat.home=/path/to/tomcat/home
 
 # uncomment to enable artifactory password authentication