MyDB Usage should be calculated based on the file size limit, not on the allocated space

[dmedv]

In CasJobs on the MyDB summary page you see something like this:
16,048 kB of 500,000 kB used
where 500,000 kB is the DB file size limit.

In SkyQuery MyDB Usage percentage on the MyDB Summary page is currently calculated based on the actually allocated space, not on the file size limit, which is not very useful.

Maybe, we should add another item to the summary ("Max DB file size", or something similar), and recalculate MyDB Usage based on that.

[dobos]

Changed logic to take max size if file is set to autogrowth, otherwise use actual file size.
What to do when size is not limited?