Enhancement: Consider a remote poll interval coming with the server capabilities

This way, admins can configure the remote sync poll interval of clients through
the capabilities settings of the server. Note that the setting in the server
capabilities needs to be done in milliseconds. Default is 30 seconds.

https://github.com/owncloud/client/issues/5947
https://github.com/owncloud/client/issues/8780
https://github.com/owncloud/client/pull/8777
