This commit adds the ability to create a new document using
existing file system browsing in the app.
Usage of StorageAccessFramework to create new document
has been ditched as it is not backward compatible.

Change-Id: I852c3de337613cb01e689d532476d2c5f932c1b3
Reviewed-on: https://gerrit.libreoffice.org/36195Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>
Tested-by: Tomaž Vajngerl <quikee@gmail.com>