Landing page to show potential proposal cycles

[DJWalker42]

We need to change the landing page to show observation proposal cycles currently offered by the various institutions, and allow the users to select the cycle to which they will be proposing.

It would be nice to show the telescopes (including operational details) associated with the distinct cycles. Notice we need to leave open the possibility of proposing to multiple cycles, potentially in different observational modes (radio, optical, etc.), simultaneously.

This may lead to being able to "configure" the GUI for different proposal cycles, the observational modes selected, and/or the combination of these things (to be done as a separate enhancement).