Proposal Clip Navigation

The Problem
When clips are far apart on a track it would be convenient to be able to move from one clip to the next. This can be extended to provide convenient clip selection, or positioning of the editing cursor at the start or end of a clip. Currently, positioning the cursor exactly at the start or end of a clip is difficult since clicking on a split line will join adjacent clips.

Proposed Feature
When the focus is in an audio track:
 * If the editing cursor is inside a clip
 * Tab moves to the end of the clip
 * SHIFT + tab moves the cursor to the start of the clip
 * ALT + tab selects from the cursor position to the end of the clip
 * SHIFT + ALT + tab selects from the cursor position to the start of the clip
 * If the editing cursor is at the start of a clip
 * Tab moves to the end of the clip
 * SHIFT + tab moves the cursor to the end of the previous clip
 * ALT + tab selects from the cursor position to the end of the clip (in effect selecting the entire clip)
 * SHIFT + ALT + tab selects from the cursor position to the end of the previous clip (selecting white space if needed)
 * if the clips abut, no selection is made and this is the same as ALT + tab
 * If the editing cursor is at the end of a clip
 * Tab moves the cursor to the start of the next clip (ignoring white space)
 * SHIFT + tab moves the cursor the the start of the clip
 * ALT + tab selects from the cursor position to the start of the next clip (selecting white space if needed)
 * if the clips abut, no selection is made and this is the same as tab
 * SHIFT + ALT + tab selects from the cursor position to the start of the clip (in effect selecting the entire clip)

Developer/QA Backing
Bill

Use Cases

 * VI user navigation of clips
 * currently there are no keyboard shortcuts for navigating or selecting clips
 * Navigating a track with many clips