Add TestResourceUnavailableException

Provides a way to skip TestNG tests if a test resource is not available (such as in the source distribution, which does not carry binary test resources)
Make embedded jars optional

Modifies code that relies on jar files as an embedded resource to
gracefully handle cases where the files are missing. Limited to tests,
which will cause TestNG to skip the test if the resource is missing.
Required for our source distribution, as Apache convention is to not
ship binaries in releases.
Make embedded wars optional

Modifies code that relies on war files as an embedded resource to
gracefully handle cases where the files are missing. Limited to tests,
which will cause TestNG to skip the test if the resource is missing.
Required for our source distribution, as Apache convention is to not
ship binaries in releases.
Merge and close #365 [BROOKLYN-29]