Upgrades target platform to 4.1.0

This upgrades the parent pom and target platform to 4.1.0-beta1.

Once this has been merged it will be necessary to:
1) Open the teiid-designer.target file in Eclipse
2) Once the target has resolved all update sites, click the 'Set As Target Platform' link at the top-right corner of the target file's editor

Building locally with maven should work without any modifications.