refactor(eapi-bash): use existing python scripts instead of redundant shims

Instead of using python shim scripts for pinspect and filter-env for
calls from the bash side we use the versions found in PATH. This is done
for non-system installed pkgcore by adding the bin directory (which
already contains the relevant python scripts) of the git repo or
unpacked tarball to PATH.
refactor(ebuild/processor): sort module imports