Removed internal/outdated/speculative docs from requirements.md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
Solved json obj to array issue
Simplified travis builds (external setup scripts)