Add target page tab for CMD

[rachel3834]

Add a view and template to build a CMD plot from an uploaded data table if one is available.
Hopefully this will be able to make use of the generic tabular data format

[KKruszynska]

Add Gaia CMD for the taget.

In principle microlensing fitting pipeline does it: https://github.com/KKruszynska/Microlensing_Fitting_Pipeline/blob/main/MFPipeline/analyst/cmd_analyst.py
Feel free to hack the interesing parts from here.