Main: make cabal unpack quiet
Setup: clean away unused options, implement --version output, cmd checking and help
Main: Package Description code moved here from Rpm, process cmd arg with pkgDesc

- so far: spec, srpm and build commands
- simplePackageDescription also moved here to Main
Rpm: bring back rpmBuild with yum install of deps; clean away old commented code

- checks for deps with rpm -q or try to install with yum install
  (yum-builddep would fail if any missing deps)
- check for tarball in cabal-install cache or cabal fetch it
- new helper functions: unlessSystem, maybeInstall, trySystem, trySystemWarn,
                        packageName, packageVersion, specFileName,
			buildDependencies, depName, showDep
- simplePackageDescription moved to Main
version 0.7.0, rename excutable to cblrpm