PHPCS: fix up the code base [1] - whitespace & inline control structures

Simple, mostly whitespace related, fixes to make the code comply with the WPCliCS rules.

Fixes relate to the following rules:
* No inline control structures (seriously ?).
* Align the equality operators in assignment blocks.
* No multiple assignments in one statement.
* One space between a control structure keyword and the open parenthesis.
* `else`/`elseif` should be on the same line as the closing brace of the preceding statement.
* One space on the inside of open/close parenthesis when there is content between them.
* One space after equality operators.
* Associative arrays with more than one item, should be multi-line.
* Each array item in a multi-line array should be followed by a comma.
* When using array indexes, use no space on the inside of the square brackets when the index is a string or integer and use one space on the inside of the square brackets otherwise.
* Use single quoted strings when the string doesn't contain a single quote or variables.
* `true`, `false` and `null` should be lowercase
* No trailing whitespace.

Author: jrfnl