Fixed boolean/integer BC break.

Booleans and integers were being inadvertently converted to strings when
saved in the config array. This preserves the datatype.
Merge pull request #5569 from michaelmoussa/readable-config-arrays

Fixed boolean/integer BC break in Zend\Config\Writer\PhpArray
[#5569] CS fixes

- elseif -> else if
Merge branch 'hotfix/5569' into develop

Close #5569
[#5569] Handle null values properly

- Previous fix led to:
  ```php
  'null' => ,
  ```
- Fix properly echoes the null value:
  ```php
  'null' => null,
  ```
Merge branch 'hotfix/5569-null' into develop

Additional fix for #5569