Trigger error when resetting password for user with empty email

When password reset is handled through verification e-mails, the
administrator should not be able to reset the password if the user's
e-mail is blank as the user won't receive the verification URL.

Fixes #15893
Issue #15893: Improve logging when resetting user password
Documentation: revised database types
Documentation: remove empty 'para' tags

These cause publican builds to fail on mantisbt.org as the tool's
version installed there deletes these tags when processing the XML,
which trigger validation errors.

Fixes #15886
Issue #15893: format user id consistently with other log messages
soap api: added wsdl-viewer

NuSoap offered a convenient, self-generated API documentation page. On
the other hand, the php-soap extension does not offer such functionality
and the wsdl's raw XML is not easy to read.

This commit adds Tomi Vanek's wsdl-viewer XSLT [1] to mantisconnect.wsdl
to offer a more user-friendly face to the XML.

[1] http://tomi.vanek.sk/index.php?page=wsdl-viewer