Improved ocrd-import

[stefanCCS]

Hi @bertsky ,
@kba has provided to me this nice (much faster) ocrd-import:
852dfbf

I just would like you give back a version, which I have improved a bit to be more compatible to workspace add.
See in this file here:
ocrd-importv2.zip
Feel free to use it, publish it, or ignore it ;-)

[kba]

I already opened a PR for those changes, cf. #23