Modifies the cohort generation & IR generation displays based on #2878. From the issue description:

1. Hover Style: if the row that you were hovering was highlighted, you could see that a generate button is associated with a source more clearly.
2. Re-arrange columns: move Generate button to first column so the button is right next to the source
3. Table Style: add borders to table to see the alignment better.

The generation buttons are moved to the left (along with other buttons since those are all in the same HTML template). In this PR, I added the hover style (see below) and opted to add the borders on hover. We could always display the border but thought this might work as well and keep the table looking clean.

Same changes were done for the IR display in this PR: