Add the reference manual from plugin_dbui_book.

.gitignore

docs/reference/conf.py

docs/reference/field.rst

docs/reference/form.rst

docs/reference/grid.rst

docs/reference/hyperlinks.txt

docs/reference/images/fr200.png

docs/reference/images/fr201.png

docs/reference/images/fr202.png

docs/reference/images/fr203.png

docs/reference/images/fr204.png

docs/reference/images/fr500.png

docs/reference/images/fr600.png

docs/reference/index.rst

docs/reference/introduction.rst

docs/reference/keypoints.rst

docs/reference/power_extjs.rst

docs/reference/preface.rst

docs/reference/radiography.rst

docs/reference/selector.rst