wot status: Use wot.requirements to get precise received certs expiration dates (#490)

Instead of unprecise computed value from wot.lookup

cross wot.lookup and wot.requirements return values,
since wot.lookup gives the uids

Delete cert_written_in_the_blockchain()

Re-add pending certs from wot.requirements
Add ✘ legend

Computed expiration due to cert expiration should not take
care into account pending certs

Remove get_sent_certifications() call
repeatedly called for no reason in a loop

Move get_sent_certifications() below