Add debug watermarks for schema report

[jng]

When previewing a feature class in the schema report, it would be very useful to inject what we know about the previewed feature class into the preview map as a watermark. Things like:

• The computed bounds
• The coordinate system used
• The number of features (this is already calculated before preview starts)

Would be very useful to have access to.

[jng]

Fixed r8007

[jng]

Fixed trunk r8009