We had a number of styles that were originally specific to the
dashboard, but later became used for other pages (such as the user
page). This included the full-page wrappers, sidebar, etc.

These are useful classes, and pages shouldn't need to pretend to be the
dashboard to get it. Those classes have now been made more generic,
with "dashboad" prefixes replaced with "datagrid."

This is really just code shuffling and renames. Nothing substantial has
changed.

Tested that all the datagrids and their functionality still worked. This

includes all the special functionality of the dashboard (batch selection,

actions, etc.), and column editing/reordering.