Permit three values:
- always (default), the other input field is always displayed
- exists, the other input field is only displayed when the setting
          contains value(s) not listed in choices*.
- never, the other input field is never displayed. If the setting
         contains any value(s) not listed in choices they will be
         discarded on saving.
* This means, under normal circumstances the admin will not see
  the other input field.  It will only appear after manual editing
  to enter a non-listed _choice or if an update were to remove a
  previously selected _choice

- replace PHP4 style class constructor function names (based on
  class name) with php 5 __construct()
Also remove some '&' reference operators used with objects
And add some object type hints

This commit consists of patches automatically generated for this project on https://scrutinizer-ci.com

In an older version of PHP a file_exists() call would issue a warning
when the file did not exist. This was fixed in later PHP releases. Since
we require PHP 5.3 now, there's no need to supress any error here
anymore. This might even give a minor performance boost.

Removed extraneous whitespace to eliminate errors reported by the
Squiz.WhiteSpace.SuperfluousWhitespace sniff.

Fix violations for Squiz.Commenting.DocCommentAlignment.SpaceBeforeTag

Conflicts:
	inc/parser/xhtml.php

Change indentation to ensure code confirms to CodeSniffer rules.

This reverts commit 0d21c87f.

replace preset _cautionList property with _caution config metadata parameter, plugins can now easily set cautions on their settings

remove php_strip_whitespace() alternate, no longer required as php min req't ensures its always present

setting type read from metadata eqaul to empty string is default 'setting' class (a textarea), everything else should be a existing class otherwise 'setting_no_class' is loaded

This deprecates the "richemail" config class

  - removed some dead/unused code
  - fixed phpdoc
  - added typing on methods

Parsing the config file should be completely tested before we can rely
on it and safely extend it. This just adds the first very basic tests.

This reverts commit b8f41ef0.

We had good reasons for parsing the file ourselves. For example to keep
expressions like 7*60*60*24 intact.