Switch albumartist_website to XmlNode

Resolves PICARD-593.

Fixes issue with #275 when run from Picard executable under Windows.
Increment version no.
Simplify display_tag_name
Use multi-value %_performance_attributes% ...

... instead of %_performance_live%, etc.

Modifies #285.
Add a test for util.tags.display_tag_name()
Merge pull request #3 from zas/test_display_tag_name

Add a test for util.tags.display_tag_name()
Fix layout (zas comments)

Note: Whilst the previous indentation of "and" was incorrect as per
PEP-8, I think it was actually more readable.
Merge pull request #301 from Sophist-UK/sophist_fix_tag_brackets

Simplify display_tag_name
Handle multiple websites
Persist log view position and size.
Merge pull request #303 from Sophist-UK/sophist_persist_log_status_dialog_size_position

Persist log view position and size.
Fix layouts again (zas comment)
Merge pull request #302 from Sophist-UK/sophist_enhance_#285

Use multi-value %_performance_attributes% ...
Merge pull request #296 from Sophist-UK/sophist_switch_albumartist_website_to_xmlnode

Switch albumartist_website to XmlNode
Add sorted versions of Performer etc.

so user can override ordinary performer with sorted version if they want
to.

Plugin to do this to be added in a second commit.
Add plugin
Add NEWS
Make plugin non-class
Switch back to standard metadata access.