Added lzmavalid plugin; disabled default intallation of bundled libmagic; updated READMEs
Updated quick install guidelines in README.md
Fixed Python3 bugs in lzmavalid and zlibextract plugins
Changed how --dumb and --invalid are interpreted by the signature scan
Added --lzma and --stop options to raw compression module
Updated compressor module to run LZMA and deflate scans simultaneously