Set current route as default route for form in getFormDesigner()

Signed-off-by: Michael 'Tekkla' Zorn <tekkla@tekkla.de>
Fixed error where $css_loaded was not set but checked.

Signed-off-by: Michael 'Tekkla' Zorn <tekkla@tekkla.de>
Made FormElement and Html classed abstract.
Changed imports on all related classes accordingly.
Changed visibilty of some properties from private to protected to
provide a way to set properties by override and not by using a setter in
the subclass.
Optimized html elements, controls, and form elements by replacing not
needed setters, factories and constructors with overridden HtmlAbstract
properties.
Changed addMethods() and addTo() method in HtmlAbstract by moving logic
of argument checking from addMethod() into addTo().
Removed not needed interface classes and removed implements and imports
from all classes accordingly.

Signed-off-by: Michael 'Tekkla' Zorn <tekkla@tekkla.de>