support quoted strings in property strings

support quoted strings in property strings

This allows free form text to exist within property strings,
quoted, like:
    key="A value with \"quotes, also commas",key2=value2
or also:
    "the value for a default_key",key2=value2

And drop ';' as a key=value separator since those are meant
for arrays inside property strings...

Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>