Scoped disabled property and class styling

[NickdeK]

Describe the bug
The disabled styling breaks other disabled styling defined in other packages/css.

For example when used with Vuetify and VWindowItem the disabled attribute makes it apply the QCalendar disabled styling showing the not-allowed cursor everywhere in that component.

To Reproduce
Steps to reproduce the behavior:

1. Add the quasar-ui-qcalendar to a project that uses another framework or already has exisiting disabled styling
2. Include the minified css or sass files
3. See the other styling being changed by the qcalendar component

Expected behavior
The styling should be scoped to only the quasar component and should not bleed out of it.