CB-4655 Makes default platform template files overridable

Better implementation for https://issues.apache.org/jira/browse/CB-4655
Updated due to @sgrebnov's [comment](https://issues.apache.org/jira/browse/CB-4650?focusedCommentId=14100327&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14100327)