[DEV] Implement the selection of a given trajectory for a s/c

[jorialand]

The usr should be able to select a trajectory from the available ones. Once all the s/c have a trajectory selected, I will be able to plot the mission timeline.

[jorialand]

The process would be as follows:

• The usr selects a row in the Earth-Mars dataframe (and Mars-Earth if appplies).
• The usr confirms the selection clicking on a btn.
  • This is handled in SonetMainWindow.clicked_tab method.
• The selection is stored as a protected attribute in the s/c object.
• A label is added in the main window indicating if a trajectory has been chosen.
• The s/c name is marked as bold if a complete selection has been made, this is, a trajectory has been selected for all its trips.
• A protected s/c attribute flag is created to control if the s/c has a trajectory chosen or not. Only if it has, the plotting phase can be performed.