Create highlights on non hypertopic-compliant Web sites

[benel]

When loaded in Porphyry:

• highlights created on Cassandre will be grouped by diaries and memos,
• highlights created on plain Web sites, will be grouped in a default corpus.

@christophe-lejeune, any preference about:

• whether the corpus depends on the user, the site domain, etc.?
• the name and/or ID of the default corpus?

For reference, in LaSuli 2, the default corpus was Marque-pages de <USER>.