Reorganize widgets
Reorganize widgets within ts_viz.py:
- add toolbar
- add one tool to toolbar (Profile): toggleable button (select/unselect tool) that needs to be selected to draw on ifg and display corresponding graph
- sub-class PlotWidget and QLabel to customize and add signals, slots, actions...
- when cursor hoovering over ifg, tooltip displays coordinates and displacement values (from current ifg)