Fix for Bug43036. Reading multiple pages in macro is slow

Add PageStore.getPages which fetches a list of pages in one SVN repository request. The request is made using SVNKit's SVNRepository.checkoutFiles method.

No SVN attributes or version information on each page is returned by
this method.

This method is intended to be used by macros that fetch a large number
of pages but do not require SVN attributes or version information about
each page.

I've tested this with a simple macro that concatenates all pages in a wiki. When the wiki has ~1800 pages the macro renders in ~40 seconds using PageStore.get() and ~1 second using PageStore.getPages().

https://bugs.corefiling.com/show_bug.cgi?id=43036