ij-ui-swing-updater: fix base package declaration
Fix reflected package names

Of course, these are all bad anyway (hence the FIXMEs), but
for now, they at least need to reference the correct FQCNs!
Rename LUTSelectorPlugin to LUTSelector

The "Plugin" suffix is discouraged, as there are many types of
plugins, and specifically, the LUTSelectorPlugin is a Command.
CommandFinderPanel: be defensive about nulls

This change guards against the possibility of the menu path's leaf
coming back null. With this change, the Command Finder UI no longer
throws NPE while browsing through the full list of commands.
populate-app.sh: skip tests when building the app

This substantially speeds up the app generation.
Revert "populate-app.sh: skip tests when building the app"

This reverts commit 71e0d8cc3b213a6a7e30fc9ee976d66e2381e84c.

Johannes requested that tests not be skipped by default, because it is
sometimes useful for them to run in certain contexts (e.g., before
uploading). But populate-app.sh accepts arguments which are passed to
the mvn executable, so you can run:

    bin/populate-app.sh -DskipTests

If you really don't want to run them.
Updater (GUI): fix ClassCastException

Repeat after me: never use magic column indices to refer to given
values. Never. Always use at least constants describing *what* you are
looking for, or, as in this case, use the appropriate method directly.

Encountered by Ruizhi Liao.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>