new feature: raw import or export and new vendor format

2021-06-22 fix: fix export on exotic dsk file.
2021-06-02 fix: fix makefile after go modules migration.
2021-06-01 fix: fix data size when sector size is different from the real sector data size.
2021-06-01 fix: fix when numberb of sectors differs from real sector number.
2021-05-31 add: add extraction from sna and import into file of existing dsk.
2021-05-31 add: add go modules.
2021-05-11 add: add amsdos header size constant.
2021-05-11 add: add auto tests in binary to ensure no bugs at runtime.
2021-05-10 fix: fix raw copy when file is smaller than 512 octets.
2021-05-10 fix: firx tracksizetable and force option.
2021-05-10 fix: fix tracksizetable in data vendor.
2021-05-04 add: add raw export data from dsk.
2021-05-04 add: add rawimport in dsk file content.
2021-05-04 add: update libs dependencies, and fix static issues.
2021-05-03 fix: export ascii.
2021-05-03 add: add vendor format.
2021-04-22 fix: fix addheader function on amsdos file.
2021-04-20 fix: fix add amsdos header on standalone file.