Added a delete history button

[vbmithr]

A new button for deleting history :)

This would be nice to put in System/App, but apparently this is not allowed for Harbour apps as it require root.

[llelectronics]

I am thinking about adding a global settings page for options like subtitle, autoplay and also remove history. So for now I won't merge it directly but will use your code when I find time to implement the settings page.

Thanks for contributing.