Add help text to workflow inputs page

Currently, an end-user who is analyzing data (launching workflows) does not have visibility into the documentation that the WDL-developers are already providing about what the workflow inputs and outputs do, what their default values are, and what they mean. Instead, currently, an end-user sees this when they are launching a workflow and being asked to configure their inputs:

Proposal: This web UI in terra on the Inputs page should add one more column to the table, or perhaps mouseover/hover text, displaying the `parameter_meta` `description` text for each input.

Also: For non-optional WDL inputs that Terra considers to be optional (because they are assigned a default value), the default value should be displayed somewhere in this table.

Rationale: this opens up a critical line of communication between WDL-developers and end-users (two different groups of people) in a way that they are already trying to do, but Terra is not displaying. Currently, if someone shops a new workflow off of Dockstore, they'd have to fish around for documentation or original source code to understand what any of the inputs even mean.

Note: this other already existing feature request talks about something unrelated at first, but later in the comments, starts to discuss this feature request. I thought I'd promote it to a top level feature request.