Decode HTML entities in WebDAV

[AliveDevil]

Some web dav implementations (currently known: Mega#2599) encode XML special characters using HTML entities, instead of percent encoding these.

We could either state that services returning invalid XML entities aren't supported, or implement the EntityResolver API, to add support for this - which would import all of Chromium/blink/html_entity_names.csv.

Failing log output:

ch.cyberduck.core.dav.SaxPropFindResponseHandler - Fatal parser error org.xml.sax.SAXParseException; lineNumber: 20; columnNumber: 32; The entity "add" was referenced, but not declared.

[AliveDevil]

i.e.

<d:displayname>C&add;&add;</d:displayname>