Release 2.6.3
Fix scrollkeeper detection

Use AC_ARG_WITH instead of AC_ARG_ENABLE, a more correct choice. Default
behavior now will use Scrollkeeper (or Rarian-compat) if it's available,
won't even try if --without-scrollkeeper is passed to configure, and
will error out if --with-scrollkeeper is passed but scrollkeeper-config
isn't found.
Improve building Japanese PDF in separate build directory.
Update revision numbers and history for V2.6.3
Help Documentation: Add Advanced Portfolio Rpt details

Committer: Chris Good <chris.good@ozemail.com.au>
Set version on master to 2.6.99
Help for budget report.

Include base description + updates for ranged report generation improvement
Merge branch 'trunk' of https://github.com/Gnucash/gnucash-docs into trunk