- Update documentation

- Remove extraneous parentheses around empty() calls
- Remove duplicate calls to intval(), count() or strlen() after empty()
- Replace ternary operators outputting binary value with empty() return value
- Rewrite defaults() without x()

update logger levels in calls

implement log() function.

This is desperately needed to fix Issue #5190.  In case of any unexpected problem, the admin can use

`$a->config['system']['sendmail_params'] = false;`

Update function names and calls for Addon class.

- Add short form array syntax to po2php.php generation

renamed some functions and adjusted corresponding calls.

Standards clean up

Create Email class and update/rename functions and function calls.

Move emailer to src Friendica\Util namespace