Deprecation docs
Removed internal/outdated/speculative docs from requirements.md
Merge pull request #1312 from chillu/pulls/deprecation-docs

Deprecation docs
Fixed path in docs
FIX Unset internal metadata on TreeDropdownField setValue()

Otherwise the hidden field value and metadata will get out of sync.
Most commonly used together with setTitle('') as well.
FIX Don't silently unset ParentID in "add page" dialog

Happened when changing the page type, because the "selectedNode"
property isn't set in all cases
API Make Object::config use late static binding

Can now be used in instance scope, like:
  $this->config()->db
and in static scope, like:
  Page::config()->db
FIX: Groups should be able to have titles longer than 50 characters (Fixes: open/5611)
Merge pull request #1334 from wilr/5611

FIX: Groups should be able to have titles longer than 50 characters
Fixed static config access in Currency and i18n (fixes #8341)
Fixed static config in BBCodeParser (fixes #8340)
FIX Clone Config_LRU incl. objects in array

Caused key confusions when using Config::nest()/unnest()
NEW Allow setting of ASSETS_DIR in _ss_environment.php
Clarified 3.1 upgrading docs
Merge pull request #1335 from chillu/pulls/config-clone-nest

FIX Clone Config_LRU incl. objects in array
Merge pull request #1336 from kinglozzer/define-assets-dir

NEW Allow setting of ASSETS_DIR in _ss_environment.php
Fixed _config.php references and usage in docs
Config docs improvement: @config and LSB mentions

Also moved some less important "notes" further down the page.
The doc is still written too much like a technical spec, we need
something that's more accessible to beginners.
Merge remote-tracking branch 'origin/3.1'
Fixed Email.admin_email config static naming