Add navigation buttons in the details view.

Add navigation buttons in the details view.

This isn't finished but I thought I'd commit what I have as it's a
pretty good start. I still need to:

1. Change the style so that it fits better into the current theme
2. Adjust the details cell to expand as much as possible.

* src/main/java/org/glom/web/client/activity/DetailsActivity.java: Add
click handlers to navigation buttons in the DetailsCells. Create a
refreshData() method to get just the data from the server without the
layout.
* src/main/java/org/glom/web/client/activity/TableSelectionActivity.java:
Update the tableSelector and browser title when the table name
changes without using the tableSelector.
* src/main/java/org/glom/web/client/ui/DetailsView.java:
* src/main/java/org/glom/web/client/ui/DetailsViewImpl.java: Rename
getDetailsCells() to getCells(). Update variable names.
* src/main/java/org/glom/web/client/ui/details/DetailsCell.java: Add
method to set click handler on navigation button. Rename a few
variables. Add navigation buttons where needed.
* src/main/java/org/glom/web/client/ui/details/Group.java: Rename a few
variables and methods.
* src/main/java/org/glom/web/server/ConfiguredDocument.java: Set the
navigation boolean and navigation table as required in the
LayoutItemField DTO.
* src/main/java/org/glom/web/shared/layout/LayoutItemField.java: Add
variables for navigation along with getter/setter methods.