Randomize sort order for available studies

[jepstein]

Story

Available studies in Core Add-on should display in some sort of random order.

[jepstein]

Should this be truly random or weighted in some way?
Do we want to prioritize showing unenrolled studies higher up?
How should current and decommissioned studies be intermingled?

Should this look like?
<(weighted?) randomized order of current, unenrolled studies>
<randomized order of current, enrolled studies>
<randomized order of decommissioned, enrolled studies>

(this all has implications for how we want to display these in the RWP)