Make the VSE Preview window a Work Area to make it easier to work with VSE

With this proposal it should be really fun and easy to do simple tasks in the blender VSE, here is a bullet point list/roadmap to make it happen

• connect sequencer and preview and make strip-objects from the sequencer selectable in the preview when visible on the current frame.

• cycle through strips under the cursor in the preview window on multiple clicks.

• make preview objects even selectable like in the viewport with alt+lmb to select layers under the current toplayer.

• when we can select objects in the preview, make these layer objects react to basic transformations like grab, rotate and scale and make it possible to constrain grab and scale to x+y (and add these values of the according strips to the transform in the n-panel of the sequencer course)

• scaling should also work by grabbing an edge of the selected object, just like render border select when the camera is active.

• using the hotkey "I" over the preview should also make it possible to keyframe scale position and rotation (and what else I forget) directly from there.

• cropping should work the same easy way of painting a rectangular selection on the currenctly active strip in the preview window, preferable with a shortcut with the letter "c" included.

Some shortcut suggestions for cropping and more ideas for functionality:

• Ctrl+C to draw the crop selection
• Alt+C to work on the selected crop with dragging the edges of the selection just like render border select when the camera is active (or the new scaling tool for VSE objects :)).
• Alt+S to scale the crop selection and Alt+G to move the crop selection.

• draw a border in default orange around selected objects in the preview

• draw a grey border around inactive objects in the preview with a bigger shape than the viewport just to indicate they are there