fix: allow Unicode object names

[mlatief]

What kind of change does this PR introduce?

Fixes #133

What is the current behavior?

Object names are restricted and Unicode non-ASCII characters are not allowed. See #133.

What is the new behavior?

Allow all Unicode characters that are also valid in XML 1.0 documents.

[TimurBas]

Would like to see this being merged @fenos. Can't upload files that has Danish letters æ, ø, å.