Refactor updated IEEG features (2/2)

This PR addresses pending issues (from PR #710) with the IEEG features.

Pending issues

[ ] Display menu (for channel file with SEEG) does something different to the stated https://neuroimage.usc.edu/forums/t/46083
[ ] Avoid closing all figures when starting a new implantation. If figures need to be closed, this must be selective: (Issue 1 in #701)
[ ] Some Java exception issues https://neuroimage.usc.edu/forums/t/46585 https://neuroimage.usc.edu/forums/t/46178
[ ] Thresholding of isosurface without creating a new one Creating of a new file was supposed to be temporary (added in #689) Discussion: Do we need this file in the DB? It will used only on localizing contacts.
[ ] Printing contact locations in GUI, better text alignment Discussion: Do we really need to print up to one-hundredth of millimeter?
[ ] Display sensors in MRI 3D slices, add isosurface to figure (surface tab), add new SEEG electrode (in IEEG tab), enable Select tool (in EEG tab), click on isosurface. Result: MRI viewer opens (why?), all electrodes disappear of GUI and Electrode configuration is disabled. Electrodes are visible in 3D figure.
[ ] Wrong CT volume can be selected thresholding CT with slider. See code: https://github.com/brainstorm-tools/brainstorm3/blob/master/toolbox/gui/panel_surface.m#L422-L426
[ ] Slider in panel surface for thresholding CT is set only at panel creation (CreatePanel), thus it's hardcoded to 1 to 4500 See code: https://github.com/brainstorm-tools/brainstorm3/blob/master/toolbox/gui/panel_surface.m#L113

[ ] Move around and edit contacts in directly in 3D view (already directly possible in the MRI viewer)
[ ] Shortcut to switch between center and non-center selection of 3D contacts
[ ] Delete and add contacts while maintaining the ordering
[ ] Regrouping contacts correctly for wrong grouping of contacts for a electrode
[ ] Sanity check for auto-detected contacts with the electrode model

@tmedani, @chinmaychinara91