Fixed lint warnings
Changed __init__ signature of Bpb class

Allow to supply filename, offset and length
Bugfix for rawstruct

If only filename is supplied, read all file contents
Ignore pdf files for now
clusters_per_mft is signed byte per Microsoft

http://thestarman.pcministry.com/asm/mbr/NTFSBR.htm

Also added property that returns mft record size in bytes
Changed Bootsector __init__ signature

Allow specifying filename, offset and length
Additional methods for rawstruct
Modified Bpb test to verify mft_record_size
Modified MftTable api