Bulk actions in job/definition list

[JasonWeill]

Problem

When users have a lot of jobs or job definitions, they cannot take an action in bulk on them. For example, deleting many jobs is difficult (see #328).

Proposed Solution

Allow users to select one or more jobs and perform a bulk action, like delete, pause, or resume, on all of them at once.

Additional context

Consider how bulk action selection should persist across pages. Should "Select all" span all items, even those that are invisible?

Server extension needs to handle bulk actions to supported API endpoints.