don't attempt ROI stats on big images

[will-moore]

If you try to run the Batch_ROI_Export script on Big images, it fails with:

> > serverStackTrace = ome.conditions.ApiUsageException: This method cannot handle tiled images yet. 
> > at ome.services.roi.GeomTool.getStatsRestricted(GeomTool.java:415) 

To avoid this, we first check for whether this is a big image and if so, we don't try to load stats.

To test, draw ROIs on a Big Image(s) and run Batch_ROI_Export script:

[imagesc-bot]

This pull request has been mentioned on Image.sc Forum. There might be relevant details there:

https://forum.image.sc/t/omero-web-script-batch-roi-export/103609/5

[imagesc-bot]

This pull request has been mentioned on Image.sc Forum. There might be relevant details there:

https://forum.image.sc/t/omero-web-script-batch-roi-export/103609/7

[pwalczysko]

Compared merge-ci with 2 rectangle ROIs on a large image with outreach (release version).

With this PR, the Batch_ROI_export works fine and produces csv outputs.
On release version of the Batch_ROI_export, an error occurrs as follows

omero.ApiUsageException: exception ::omero::ApiUsageException
{
    serverStackTrace = ome.conditions.ApiUsageException: This method cannot handle tiled images yet.
	at ome.services.roi.GeomTool.getStatsRestricted(GeomTool.java:415)
	at ome.services.blitz.impl.RoiI$8.doWork(RoiI.java:260)
	at sun.reflect.GeneratedMethodAccessor295.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:333)
	at