#12 add element dialog description segments

[CSchmitz81]

Finished changes for #12 (incorrectly indicated this was for issue #23 in last commit & branch name), with the following new issues needed:

• Improve description config variation updating #39 save description variation after done deleting & moving segments around
• Add save prompts for edited description segments #40 need prompts to wait or save when switching edited item, segment variation, switching element views, or closing element dialog
• Use template stamping for procedurally created elements #41 update ctree-description to use template stamping (and data binding) instead of manual element creation
• Moving description segments resets current variation #42 when switch segment variation, doesn't persist when moving segments around
• Add segment type selection #43 when press + buttons show prompt to select segment type
• Add prompt for reason creating new description segment variation #44 prompt reason for new segment when saving
• Add option to save changes for later #46 add option to save changes for later