Group Travis CI jobs in stages (#5104)

- This should speed-up Travis CI tests and refers to #5049

- Travis uses build-stages to group tests together
    - The idea is to let fast tests fail first, then move to longer ones.
    - Added external perl to avoid download failure from CPAN and reduce build time
    - Disabling perl-dbi: continues to fail with (504 Gateway Time-out) on Travis

- We now cover all the build systems in tests:
    - Add back `openblas` to Travis as a separate package.
    - Switched `openblas` for `astyle` to build a simpler MakefilePackage.
    - Added 'tut' (WafPackage)
    - Added 'py-setuptools' (PythonPackage)
    - Added 'perl-dbi' (PerlPackage)
    - Added 'build_systems' directory to the ones for which we get a summary
    - Added 'openjpeg' (CMakePackage)
    - Added 'r-rcpp' (RPackage)
    - Added comments to build tests to show the covered build system

var/spack/repos/builtin/packages/r-rcpp/package.py

@@ -39,6 +39,8 @@ class RRcpp(RPackage):
     homepage = "http://dirk.eddelbuettel.com/code/rcpp.html"
     url      = "https://cran.r-project.org/src/contrib/Rcpp_0.12.9.tar.gz"
 
+    version('0.12.12', '97b36a3b567e3438067c4a7d0075fd90')
+    version('0.12.11', 'ea1710213cbb1d91b1d0318e6fa9aa37')
     version('0.12.9', '691c49b12794507288b728ede03668a5')
     version('0.12.6', 'db4280fb0a79cd19be73a662c33b0a8b')
     version('0.12.5', 'f03ec05b4e391cc46e7ce330e82ff5e2')