Add support for reading from TAR archive

[VeaaC]

Flatdata archives are currently stored as dictionaries. For distribution it could be much nicer if they instead were a single file.

I propose that we should add support die the ResourceStorage(s) of the different languages read from (memory mapped) TAR archives

[VeaaC]

Waiting for the tar crate to release the Seek improvements ( alexcrichton/tar-rs#218 ) before updating dependency version and closing this one.