Creating a new issue bases the next id only on the filtered issues.
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Problem
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This represents a more systematic error. Filtering should be applied when
viewing the data only, not when loading the data. It is possible that
operations may need the full data to modify parts of it.

Solution
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Remove filtering fromt he project and issue construction. Double check that
filtering is correctly applied during all the access methods (eachIssue,
eachProject, each)

Testing
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Updated ProjectTest.testConstruction() to reflect changes.

Added a test to ProjectTest.testCreateNewIssue() that needs to count a closed
task to correctly generate a new id.

TODO: Need to create filter tests.
