util::file_content_check: new utility for checking content of a file
Check whether the provided file is of the requested type. This function is more robust and protable than relying on external programs and their output, but it does not work on all possible file types. It checks a few common cases that could lead to problems otherwise, like when uploading archives.
- Feneralized flag "-no_empty" of "LockfreeCache eval" to "-no_cache LIST" The provided list can contain multiple values that should not be cached. - The new parameter "-from_cache_indicator" can be used to return information whether the returned value was returned from the cache or not.