Combined the apps.Driver class into apps.Fop. (195 LOC total.) Primary

Combined the apps.Driver class into apps.Fop. (195 LOC total.)  Primary
benefit is to make Fop self-documenting in external code, also none of the
API ideas called for retention of the Driver class (even if there were
different ideas for its replacement).

Let's try this for a few weeks, if it confuses people too much (or when
the API starts to grow again) we can bring back Driver, possibly under
a different name, apps.FopProcess, perhaps.

See also:
http://marc.theaimsgroup.com/?l=fop-dev&m=108947697611032&w=2
http://marc.theaimsgroup.com/?l=fop-dev&m=108966015504506&w=2
http://marc.theaimsgroup.com/?l=fop-dev&m=108942673103344&w=2
http://marc.theaimsgroup.com/?l=fop-dev&m=108958756030147&w=2

git-svn-id: https://svn.apache.org/repos/asf/xmlgraphics/fop/trunk@197827 13f79535-47bb-0310-9956-ffa450edef68