[banquepopulaire] Scrapping invests & liquidities from Lifebourse

Re-added the Investments class to lifebourse/pages.py
Modified banquepopulaire browser to scrap 'TIT' but also 'PRV' accounts
Modified banque postale browser to avoid scraping liquidities and avoid
redundancies.

The previous Banque Populaire code only scrapped accounts starting with
'TIT', this was modified since accounts starting with 'PRV' also appear
in Lifebourse with invests and liquidites.
An 'XX-liquidity' class was re-added to the pages files of Lifebourse,
since Banque Populaire customers wanted liquidities to appear. The
browser file from Banque Postale file was also modified to prevent
liquidities from appearing since it would be redundant with current
accounts.

Closes: 5162@zendesk