[parrot] use nqp-p instead of nqp
[JVM] use "install" prefix, and nqp-j
avoid variable name collisions
[parrot] use nqp-p, really.
[build] shuffle around stuff from the Makefiles a bit
[build] avoid collision of HARNESS_WITH_FUDGE
(mostly) import NQP::Configure from nqp
start to fold ConfigureJVM.pl into Configure.pl
fix parsing of nqp-j config
more Makefile fiddling
unconfuse perl6-j runner
toss ConfigureJVM.pl
avoid collision in src/gen/main.nqp
unentangle CORE_SOURCES
[build] more fiddling

now "make j-test p-test" builds rakudo-j and rakudo-p
and runs their tests successfully, without any interferences.
[build] generate some catch-all targets
build convenience perl6 "executable"

also enable make $single_test_file
[build] get rid of the last few Makefile rule collisions
unbreak --gen-nqp=$branch
[Configure] fix help text