Added a set of UNO accessibility roles for specific kinds of
documents:
 * DOCUMENT_PRESENTATION for Impress
 * DOCUMENT_SPREADSHEET for Calc
 * DOCUMENT_TEXT for Writer

The other applications still use the existing DOCUMENT role.

These roles translates directly to ATK but in the other toolkits we
keep using the same association that DOCUMENT role had.

Change-Id: Ibac47527e5effdecb28d2314cde8558cf4fb010a
Reviewed-on: https://gerrit.libreoffice.org/7847Reviewed-by: Michael Meeks <michael.meeks@collabora.com>
Tested-by: Michael Meeks <michael.meeks@collabora.com>