fix(pageowner): allow unsetting of page owner guid

fixes #7278
Merge pull request #7345 from jdalsem/unset-page-owner-guid

fix(pageowner): allow unsetting of page owner guid
docs(design): added the data model image from docs

ref: #7552
docs(general): moved pronuncation file from docs

ref: #7552
chore(docs): replace hardcoded link to learn.elgg.org with internal
reference

ref: #7552
Merge pull request #7593 from jeabakker/leftover-docs-issue

Leftover docs issue
chore(uservalidationbyemail): change ['login:after', 'user'] to ['login:before', 'user'] event
Merge pull request #7602 from iionly/issue-6493-3

chore(uservalidationbyemail): change ['login:after', 'user'] to ['login:...
docs(support): added documentation about the support policies of Elgg

fixes: #7581
fix(likes): Uses getDisplayName() instead of assuming the object has value in title property
Merge pull request #7620 from juho-jaakkola/likes_target_title

fix(likes): Uses getDisplayName() instead of assuming the object has value in title property
Merge pull request #7609 from jeabakker/support-policy

docs(support): added documentation about the support policies of Elgg
fix(views): correctly close the comment form contents
Merge pull request #7624 from jeabakker/comments-form

fix(views): correctly close the comment form contents
fix(notifications): Verifies that a notification method is registered before using it

Instantly sent notifications now respect the registered notification methods instead
of assuming that a method is available only because it can be found from user's
notification settings.

Fixes #7647
Merge pull request #7648 from juho-jaakkola/verify_notification_methods

fix(notifications): Verifies that a notification method is registered before using it
Merge branch '1.9' into 1.10
Merge pull request #7674 from mrclay/merged_19

Merging 1.9 into 1.10