12018: Several changes, listed below:

12018: Several changes, listed below:
* Removed initial Python version.
* Removed superfluous input files checks and moved file opening
to be before any API calls, to avoid doing them is there's a problem
with the file.
* Added user, group & link types so they're populated by json decoding.
* Cleaned up ListAll() func so it can work with different resource
types.
* Changed usage of set style types from map[string]struct{} to be
map[string]bool to simplify membership checking.
* Corrected error messages to start with lowercase.
* Added more debug messages for -verbose mode.

Arvados-DCO-1.1-Signed-off-by: Lucas Di Pentima <ldipentima@veritasgenetics.com>