Support loading custom legend files

[jcfr]

Remove custom table management:

• Support for direct loading of CSV file into Slicer. Once a file is loaded, this would create a vtkMRMLTableNode
• Re-use the node selector associated with vtkMRMLTableNode.
• Add "Import legend" button to the UI. Once the table node is imported it would be associated with an attribute like Q3DC.TableLegend ensuring only the relevant node are listed in the selector

Approach 1

• Keep the current CSV format with the region, and implement filtering of table value per-region

Approach 2

• Change the "legend" format so that we have one file per "region".

Instead of one file called base_fiducial_legend.csv, we would have the following files:

• CRANIAL BASE.csv:

Region,Landmark,Name
CRANIAL BASE,Ba,Basion
CRANIAL BASE,S,Sella
CRANIAL BASE,N,Nasion

• NASOMAXILLARY COMPLEX.csv:

NASOMAXILLARY COMPLEX,A,A-point
NASOMAXILLARY COMPLEX,ANS,Anterior Nasal Spine
[...]

• MANDIBLE.csv:

MANDIBLE,B,B-point
MANDIBLE,Pog,Pogonion
[...]

cc: @aruellas

[bpaniagua]

Approach #1 was selected during our last meeting.

[luciacev]

@bpaniagua @jcfr
Thanks for your work on this open issue.
Nothing happens when I click on the Select legend button, No menu open. I tired to drag and drop a csv file with landmark legend but the select legend button does not seem to work. Thanks
Lucia