Coordinate data in morphology sub-package saved as text file

**Is your feature request related to a problem? Please describe.**
#1652 

**Describe the solution you'd like**
Instead of saving lists of coordinates to the output csv file where other extracted traits are stored, update the behavior in v5 to optionally save coordinates to text file. 


**Additional context**
`find_tips`, `find_branch_pts` are the two functions needing updates. 