Lower the default for page.index.macro.max.pages

There is currently a system property page.index.macro.max.pages  in Confluence Server for setting the max number of pages that will be displayed by the page index macro.  The default for this system property is currently set to 5000 but it seems that for some customers this is too high.  We should lower the default to mitigate against further outages as a result of this macro.

A default of 500 or 1000 tops should be sufficient but some testing of the memory usage on large spaces should give us a good signal of what to go with.