As we want more widget themes added in the future, add the content
of theme_definitions to its own "ios" folder (as it is a theme
mimicking ios look&feel).

Change-Id: Ie435263c3861aaa324e02cfe955b8288211b2888
Reviewed-on: https://gerrit.libreoffice.org/69313Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>
Tested-by: Tomaž Vajngerl <quikee@gmail.com>