Create separate methods for the import steps.
split off EMX metadata parser from the importer
Delegate validation to the parser.
import packages after entities
Split off the transaction callback into EmxImportWriter.
Call DDL statements on another thread in another transaction since MySql implicitly commits them as soon as they succeed.
Move the try/catch and the schema changes rollback
to the EmxImportWriter as well.
Toss away the executor thread if it is no longer in use.
share the async jdbc template to keep the total number of threads in check
Merge pull request #2108 from fdlk/feature/transactImport

Feature/transact import
Merge branch 'master' of https://github.com/molgenis/molgenis

Conflicts:
	molgenis-data-mysql/src/main/java/org/molgenis/data/importer/EmxImportService.java
Fix tests, merge with master