create and .gitignore gen/{parrot,jvm,moar}
[parrot] build stage{1,2} in gen/parrot/
[parrot] generate nqp in gen/parrot/

currently that nqp is only invocable from gen/parrot/;
need to fix that before the build can succeed
unbust the build

"make test" does not work though
executable name nqp-p
move nqp-config to gen/parrot
fix bootstrap-files
create a ./nqp launcher
build NQP launcher by default; use it in test runs
fix installation

also split up "install" in "base-install" and "exec-install".
The former installs the binary as nqp-p, the latter as nqp as well
try to generate nqp.bat launcher for windows
[JVM] move some generated files to gen/jvm/
[Parrot] missing cleanup
factor out common definitions from the Makefile-$backend.in files to a Makefile-common.in
[moar] start to move generated files to gen/moar
[moar] move moar generated files to gen/moar/
[parrot] get rid of useless gen/ subdirs

now that we build stuff in gen/parrot, it is redundant

also clean up cleanup list
[JVM] remove useless gen/ dirs

that stuff is in gen/jvm/ anyway
[parrot] start to rename Makefile variables

the idea is to join the various Makefiles eventually, so we should avoid
name collisions.

No functional changes
put more variables into Makefile-common.in