This is an usability enhancement.

Current situation: when inserting an image or object, the Alternative text, Description text and decorative checkbox are not filled. 

To comply with a11y, user need to fill data later.

Suggested enhancement:

1) Add a parameter (checkbox) in Writer Options to force a dialog to get a11y data when inserting images/object.
- when checked, call a dialog to get a11y data when inserting and image/object (see 2)
- when not checked, do not call a dialog to get a11y data. This is the current behaviour.
- Factory default is non-checked (current behaviour)

2) Create a dialog to get a11y properties of the inserted object
- The dialog shall open when the Open/Insert button of the image/object file picker dialog is clicked,
- the dialog shall ask for a11y properties as in the object a11y properties dialog tab
   -- Name (allow override suggested name, check for unique name)
   -- Alt text
   -- Description
   -- Decorative

- The OK button shall add the inserted data in the object a11y properties 
   - The dialog controller shall check for name uniqueness and return to dialog if duplicate name is entered. A error prompt must indicate duplicate name.

- The Cancel button shall skip the a11y data insertion.
   - the suggested name is inserted (the name is unique
- after OK/Cancel is pressed, the image/object is inserted in document