PDI-2875 - Environment Variables in Text File Input Error Handling doesn't work

Test case and cleanup
PDI-2875 - Environment Variables in Text File Input Error Handling doesn't work
PDI-10948 - JSON Input step suppresses errors
PDI-11804 - Microsoft Excel Writer step errors out with a misleading error message when the sheetname is longer than 31 characters
Merge pull request #484 from pavel-sakun/PDI-10948

PDI-10948 - JSON Input step suppresses errors
Merge branch 'master' of https://github.com/pentaho/pentaho-kettle
Merge pull request #495 from mattyb149/master

[CLEANUP]: Add core plugins to checkstyle coverage
Merge pull request #476 from pavel-sakun/PDI-2875

PDI-2875 - Environment Variables in Text File Input Error Handling doesn't work
Merge branch 'master' of https://github.com/pentaho/pentaho-kettle
Merge pull request #490 from pavel-sakun/PDI-11804

PDI-11804 - Microsoft Excel Writer step errors out with a misleading err or message when the sheetname is longer than 31 characters
Merge branch 'master' of https://github.com/pentaho/pentaho-kettle