Test cases for the Elf Header

-> Identified bug in MAGIC
Validate the header generated by ElfFile

Previously ElfFile relied on a valid header being passed in. This has
bene changed, and it will now generate its own header.

ElfHeaderX86_64 has been enhanced to provide a static generator for
object files. In the future this will need to be extended to support
other file types.

Bugs where incorrect information was being written to the header have
been fixed

Fixes #27