[rbp] Add screenshot implementation that includes video layer

As Pi doesn't use GL for video, a screenshot only contains UI.
Need to use Pi specific function for screenshot.
First implementation of the CRenderCapture interface

RenderCapture implementation for RPi using DispmanX

Minor changes that I reverted to the repo's version

Changed snapshot taking to use g_RBP.CaptureDisplay()

Removed unused fields, and changed implementation to use the width and height parameters
Use utf8 for text pasted from the clipboard
Remove 'Go to settings' Context menu from FileManager
Dont show 'Select all' in context menu, if everything is already selected
Merge pull request #3053 from jhsrennie/paste_utf8_2

Use utf8 for text pasted from the clipboard
Merge pull request #2807 from Fice/filemanager_context_cleanup

[Context Menu] Filemanager context menu cleanup
Merge pull request #3023 from popcornmix/screenshot

[rbp] Add screenshot implementation that includes video layer
Merge pull request #3020 from brooc/master

RenderCapture implementation for RPi