#164 Create test item aggregates

[Glen Lewis]

Create a new object for reporting called a "Test Item
Aggregate". This will be automatically created in the
test plan or wherever based on a new column in the
manual test plan, the "AggTag" column.

Basically if there is a value in this column a new
TestItemAggregate object is created, and the test item
is inserted into a collection in this new object.

When the test session has completed, the test item
aggregates (themselves in a collection) will be made
available to the velocity context for reporting.

Should be a piece of cake and improve integration into
TCDB.

[Glen Lewis]

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Make sure we know how this needs to be used, since entries
in a test plan get expanded into many test items. Is a test
item aggregate supposed to be specific to a node or sliced
up some other way?