Add export / import of theme settings

[Manoj Solanki]

It would be very useful if there was an import / export option for theme settings.

[Info 3bits]

This option already exists using a 3rd party block: https://moodle.org/plugins/block_admin_presets

Some themes already include this option and would be really useful having more 400 settings.

We could try to add this block in Adaptable

[Manoj Solanki]

This has been integrated via https://bitbucket.org/covuni/moodle-theme_adaptable/pull-requests/63/property-settings/diff