TODO doc for GConf.PropertyEditors namespace.

There are in total 13 xml to document in GConf.PropertyEditors. Right now there are 13 xml not documented in any proportion.
The idea is to have a easy way to know what documentation is missing, if you want to help or are helping please take out the xml that you commit
from the missing list. For documentation that take some time to finish (like HTML, TextBuffer, etc) the best is that you but your name and email
next to the file in this list to acknowledge that you are working in it (is recommendable that you suscribe to the mono-docs  mailing list).

Following is the list of undocumented xml:

EditorNotSupportedException.xml
EditorShell.xml
InvalidGladeKeyException.xml
PropertyEditor.xml
PropertyEditorBool.xml
PropertyEditorColorPicker.xml
PropertyEditorEntry.xml
PropertyEditorEnum.xml
PropertyEditorFileEntry.xml
PropertyEditorOptionMenu.xml
PropertyEditorRadioButton.xml
PropertyEditorSpinButton.xml
PropertyEditorToggleButton.xml
