Better handle long lists of soft credits on transaction entry pages

Currently, you can soft credit as many constituents as you like per transaction. However, in cases when when you receive a pooled gift (eg from United Way or a workplace giving system) with many constituents the list can get so long that it's hard to view the Edit Donation screen and the page might take a while to load.

Improving the user interface to support long lists of soft credits could make viewing transactions with many soft credits easier because the page would load faster and require less scrolling.