Added preliminary support for DSN. Refs #4396
Fix reference to parseDsn method
Group all unset calls together
Remove Hash class dependency
Simplify DSN logic in ConnectionManager
Fix doc comment variable reference
Update doc comment
Update docblock comment
Set config argument default value to null
Use upper-case DSN everywhere
Remove extra single quote
Standardize on setting 'username' and 'password' keys

CakePHP users a variety of names for these keys internally, though the most widely recognized are the above, so it makes sense to standardize on them.

Note that we remove the `user` and `pass` key from the $parsed config instead of the $config as it is possible to have them in a querystring argument.
Simplify usage of parseDsn

parseDsn can now be used mostly out of the box by all classes using the StaticConfigTrait - with the exception of ConnectionManager, as noted below. Unless they are otherwise specified, the `scheme` of the DSN is set as both the `className` and `driver`. As such, the preferred method for usage in your application would be:

    Fully\Namespaced\ClassName://username:password@host:port/path?query=string&args=here&driver=Some\Other\Class\Name

This commit drops support for `scheme+Namespaced\ClassName\As\Driver`, simplifying the underlying logic a bit.

For the ConnectionManager class, Drivers still need to transform the path into a database_name, and as such we cannot use the trait method as is.
Working getClassMap() changes
Fix PHPCS violations
Trying to improve some doc blocks
Fix docs and variable names.

Add missing docs and fix gross klassName vars.
make it possible to modify the dsn class map

Use a static property, and put a get/set method for it into the static
config trait.
Merge remote-tracking branch 'origin/3.0' into 3.0-dsn-support

* origin/3.0: (172 commits)
  Consolidate doc block headings.
  Adding a test for https://github.com/cakephp/cakephp/pull/5019 the plugin view file path
  Fixing the view file loading for plugins in View/View.php
  Make method name better represent what it is going to do.
  Don't mutate cwd.
  More doc block corrections.
  Cosolidate doc block headers
  Add FlashComponent property to PHPDoc for Controller class
  Fix doubly inflected variable names in controller task.
  Use chdir() instead of calling multiple commands.
  Add missing 'b' to radio docs
  Fix FormHelper::radio() options docs
  Add test case for quoted strings
  Fix issue in PoFileParser where only slashes from translations of type array are stripped.
  Remove for attributes for other group type inputs.
  Remove meaningless and possibly wrong for attr.
  Fix missing label elements in input(type=radio)
  Fix radio widget and label=false.
  Fix input() making multiple checkboxes.
  Not using union, but OR conditions
  ...
Consolidate doc block lines around chaining.