Changed to using ImportPackage parser.
Merge pull request #2 from maier49/use_import_package_parser

Changed to using ImportPackage parser.
Cleaned up importer interfaces and added Builder pattern to entities.

Provided an 'AbstractFileImport' for the scala implementation to derive from more simply.
 Also added new spock tests for `entity` package.  More to come for the importation engine.
Refactored and added Export-Package header parser

* Renamed parsers to more clearly indicate what they parse.

* Moved test cases to the appropriate package.

* Implemented Export-Package header parser and added unit tests
for it.

* Moved common functionality for parsing imports and exports to
a separate object.

* Used new export parser in ScalaFileImporter.

* Added null checks to avoid NPEs in parsers.

* Fixed typo in FileImporter javadoc comments.
Merge pull request #3 from maier49/refactor-and-add-export-parser

Refactored and added Export-Package header parser