docs(actions): Migrated actions section from old Getting Started docs and cleaned up related sections.

Refs #6812.
docs(events): Updated event list and cleaned up existing event docs.

Refs #6812.
docs(hook): Updated hooks docs.

Refs #6812
docs(all): Added getting started for developers.

Refs #6812
docs(all): Cleanup docs.

Refs #6812.
docs(admin): Migrated Getting Started guide from wiki.

Refs #6812.
docs(faqs): Started migrating some FAQs.
fix(relationships): distinct ege* results when relationship_guid is not set

elgg_get_entities_from_relationship() was returning duplicate entities when
relationship_guid was not set. This was likely caused by MySQL optimizing
the query and using a different index to fulfill the r.id select.
Specifying group_by in cases where relationship_guid is not set fixes the issue.

Fixes #5775
fix(i18n): grammar fix in upgrade warning

fixes #6961
Merge pull request #7330 from hypeJunction/disctinct_ege_rel

fix(relationships): distinct ege* results when relationship_guid is not ...
docs(menus): improve docs for menu item factory

Clarifies that the 2nd argument for elgg_register_menu_item() is used
as the arguments for ElggMenuItem::factory() and the options PHPdocs
are moved to factory().
Merge pull request #7348 from mrclay/menuitem_docs

docs(menus): improve docs for menu item factory
fix(uservalidationbyemail): makes emailsent page public

Marks uservalidationbyemail/emailsent as a public page in walled garden to
ensure that newly registered users receive a understandabe comfirmation page.

Fixes #7334
Merge pull request #7358 from stianlik/uservalidationbyemail

fix(uservalidationbyemail): makes emailsent page public
Merge pull request #7240 from brettp/docs_getting_started

Docs getting started
fix(access): always display readable access level for ACCESS_* constants

Labels for global ACCESS_* constants should always be meaningful,
and not Limited. Most obvious example is when write access arrays
are not populated with ACCESS_PUBLIC in a walled garden mode.
Or else when certain global access levels are filtered by hooks
for a select group of users

Fixes #6801