0.5.15 RC1

changes:

- improved storage of protected API features
- code cleanup

new features:

- added screen protection
- added default values for mobile

fixes:

- background color of the textarea in the settings export was not readable in the dark theme when the value was invalid
- settings sanitation: added missing APIs
- navigator.oscpu and navigator.buildID are undefined in non Gecko browsers
- resetting the settings had undesired side effects
- added window.open protection

known issues:

- if a data URL is blocked the page action button does not appear