remove PonyDocsExtension::ClearNavCache() and all callers for WEB-9092 +review WEBCR. this is safe because we now call the working PonyDocsProductVersion::ClearNAVCache() as part of the TOC save hook.
code convention tax for WEB-9092 +review WEBCR-299
Merge pull request #16 from splunk/dev-WEB-9092

Remove orphaned and confusing PonyDocsExtension::ClearNavCache() method