Ignore xtend ._trace files.
Revert "Ignore xtend ._trace files."

This reverts commit 27a42c59d72db38d0a52d4f95bb6bd1b4fad12b8.
Ignore xtend ._trace files.
Implemented scope for Features's classifier and prototype reference.
Make error manager settable for testing
Updated flow latency analysis test to account for changes in CVS output
When testing scopes, do not depend upon the order of the identifiers.
Also, when testing scopes of property set elements, filter out the
property sets that are in the Plugin_Resources directory, but not
predeclared properties.
Fixed special features
Data classifier for event data source is optional
Data classifier for event data source is optional - merged UML model
When testing scopes, filter out packages in the Plugin_Resources
directory.  Also changed expected parameter of assertScope() to be a
list of strings instead of a single string.
Make classifier references for special features work - fixes #424
Merge remote-tracking branch 'upstream/develop' into develop