add an introductory table containing all options of the basic form type
document the options inherited from the BaseType class
document the auto_initialize option for the form type, refs #3410
removed the description of the auto_initialize option from the button type reference docs
minor #3611 [Reference][Forms] add an introductory table containing all options of the basic form type (xabbuh)

This PR was merged into the 2.3 branch.

Discussion
----------

[Reference][Forms] add an introductory table containing all options of the basic form type

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets |

Commits
-------

b3ca94c removed the description of the auto_initialize option from the button type reference docs
58170fe document the auto_initialize option for the form type, refs #3410
2ca0306 document the options inherited from the BaseType class
911cc70 add an introductory table containing all options of the basic form type