BUG: fix regular expression for key=value pairs where value contains special characters

This MR fixes a bug in the extended XYZ parser for key=value pairs containing special characters, e.g. keyname=file.xyz@0.

The regular expressions have been generalised to allow anything except whitespace in the value string for key=value and anything at all in key={value} or key=“value”. A new test case has been added to prevent regressions.

The MR also allow partially addresses issue #53, as keys can now contain hyphens.