admin-guide/basic: finish client requirements

Signed-off-by: Dunrong Huang <riegamaths@gmail.com>
admin-guide/basic: finish GUI interface

Signed-off-by: Dunrong Huang <riegamaths@gmail.com>
admin-guide/data-center: start writing date-center documentation.

align fix!

Signed-off-by: Dunrong Huang <riegamaths@gmail.com>
admin-guide/data-center: finish introducing date center

Signed-off-by: Dunrong Huang <riegamaths@gmail.com>