Rename Field to DetailsCell.
This is a refactor-only commit. No functionality has been added or
removed.
* src/main/java/org/glom/web/client/activity/DetailsActivity.java:
Update variable and method names.
* src/main/java/org/glom/web/client/ui/DetailsView.java:
* src/main/java/org/glom/web/client/ui/DetailsViewImpl.java: Update
variable and method names.
* src/main/java/org/glom/web/client/ui/details/DetailsCell.java:
Renamed from Field.
* src/main/java/org/glom/web/client/ui/details/Group.java: Update
variable and method names.