Fix bug in area deletion fix.
Merge branch 'release_30' into release_31

Fix bug in area deletion fix.
Merge branch 'release_31' into development

Fix bug in area deletion fix.
Add new clang-format for new code.
Add PackageModel and tests.

It currently doesn't do anything and doesn't even depend on package.
Have PackageModel inherit from QAbstractItemModel.

This includes stubs for all of the required functions with safe,
implementations which do nothing.
Depend on package/package_item from mudcore.
blah
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