Changed the external interface so that the calls take a void * rather than exposing the internal file_ent *
Moved the ext file entry object to a much cleaner single cursor implementation and added an abstraction layer for reading/writing and loading/storing.  Can now handle multiple buffer sizes.
Added clean unmounting checking
Added file truncation routine (untested) and tidied a few more cases in open()
Added new block creation in select_buffer() and md5 checking of the binary read test