Supress android-lint warnings about base Activity classes.

DocumentActivity and TableDataActivity should not be in the manifest,
so suppress the android-lint warnings.
Manifest: Mention TableListActivity (used on small screens only).

Noticed by android-lint.
Make some fields private.

Noticed by android-lint.
Remove now-unnecessary throws declaration.

Noticed by android-lint.
Remove now-unnecessary imports.

Noticed by android-lint.
Make some variables final.

Noticed by Android Studio's inspect code feature.
Remove useless checks for this == null.

Noticed by Android Studio's code inspection.
This was probably left over from some automatic refactoring in Eclipse.