feature(groups): Added featured groups as a tab along with groups, popular, discussions

Slightly changed and combined work of @thuvalpakshi
fix(notification): extract notification summary from $params

Fixes #6885
fix(river): add enabled col to river table, update on enable/disable of referenced entities

Fixes #6022 - empty river items fetched when referenced entities are disabled
Merge pull request #7013 from beck24/6022-empty-river

fix(river): add enabled col to river table, update on enable/disable of ...
fix(core): output/iframe made to the w3c standard

Not all browsers support the self closing iframe tag, according to the
w3c standard it's not self closing.
Merge pull request #7040 from jeabakker/iframe-w3c-standard

fix(core): output/iframe made to the w3c standard
fix(upgrade): use correct table prefixes on river upgrade script

Fixes #7033
Merge pull request #7053 from beck24/7033-dbprefix

fix(upgrade): use correct table prefixes on river upgrade script
chore(i18n): update translations
chore(release): v1.9.0-rc.5
Merge pull request #7057 from beck24/release-1.9.0-rc.5

Release 1.9.0 rc.5
docs(contribute): Updated recommendations on which branch to submit against

Fixes #6964
fix(pages): Stop registering undefined upgrade event callback

Fixes #6780
Merge pull request #7061 from ewinslow/pages-upgrade-warning-b6780

fix(pages): Stop registering undefined upgrade event callback
Merge pull request #7060 from ewinslow/docs-branches-b6964

docs(contribute): Updated recommendations on which branch to submit against
chore(js): configure package.json for simpler JS testing
fix(js): elgg.normalize_url no longer modifies urls that begin with a recognized scheme

Fixes #6000
Merge pull request #7065 from ewinslow/normalize-url-b6000

fix(js): elgg.normalize_url no longer modifies urls that begin with a recognized scheme
docs(notifications): Adds docs for  'object', 'action' and 'summary' params used by notify_user()
Merge pull request #7066 from juho-jaakkola/notification-summary

Extract summary from $params in notify_user()