Make isValid* calls of configuration forms being static

This allows a more flexible usage as there is no need to access instance
formdata when validating such configuration.
Let the form decide where to get the resource configuration from

refs #7163
Add some redundancy to get more implicitness

Although this commit does not seem reasonable
at first the "big" picture proves its necessity!

refs #7163
Make the loglevel ERROR being the default

refs #7163
Make it possible to retrieve a list of available users for authentication

refs #7163
Add some more platform related calls

refs #7163
Fix that ldap auth validation does not send a BIND request
Improve form element description
Silence stat() call
__toString() should call __toString() as well if possible

There may be cases that an error occurs and another _toString()
implementation handles that appropriately. This is such a case.
Populate a wizard page in case the user moves backwards

refs #7163
Improve page permission handling

refs #7163
Add utility to ease working with databases without the use of Zend

refs #7163
Add container to store and handle installation requirements

refs #7163
Add welcome page

refs #7163
Add requirements page

refs #7163
Add authentication page

refs #7163
Add preferences page

refs #7163
Add DbResource page

refs #7163
Add LdapResource page

refs #7163