fixes JOO-85
"EXML gridColumn generates config class without gctype"
http://jangaroo.myjetbrains.com/youtrack/issue/JOO-85

Now, *every* config class has a non-null ConfigClassType, there is
a new type for <exml:class> (which was formerly represented as
null) and all types are named like the corresponding EXML elements.
The mapping from EXML root node name to ConfigClassType has
moved into ConfigClassType.fromExmlRootNodeName(), as has the
flag whether to use config objects or instantiate EXML objects of
that type immediately (ConfigClassType#isCreatedViaConfigObject()).
This flag is only false for CLASS and GRID_COLUMN.
fixes jangaroo-tools part of JOO-86
"Allow EXML plugins to access their hosting component"
http://jangaroo.myjetbrains.com/youtrack/issue/JOO-86

Any <exml:plugin> without an explicit super config class now inherits
from ext.config.plugin (to be created in jangaroo-libs/ext-as).

While at it, also introduced default super config classes for
<exml:component> (ext.config.component),
<exml:class> (joo.JavaScriptObject),
<exml:layout> (ext.config.containerlayout), and
<exml:gridColumn> (ext.config.gridcolumn).