Fix "Show in Journal" functionality - Fixes #4777

When one activity want show a object in the journal, should shw the detail view,
but was showing the list view.

Signed-off-by: Gonzalo Odiard <godiard@sugarlabs.org>
Merge pull request #379 from godiard/fix_4777

Fix "Show in Journal" functionality - Fixes #4777
Fix display of multiple alerts in home view - Fixes #4757

Copy the logic on grphics/window.py to avoid display more than one
alert at the same time.

Signed-off-by: Gonzalo Odiard <godiard@sugarlabs.org>
Show the Join option in the activity palette in neighborhood - Fixes #4779

The default value when the activity is not configured is 0, not None