The main change is that `test_all.py` is now renamed to `run_suite.py`,
with the latter being able to run a selected test suite if a corresponding
command line argument (test suite directory name) is provided.
CMakeLists are improved to copy each test suite separately to avoid
copying unnecessary files. Also each test suite corresponds now to
a separate CMake test.
All imports inside the test cases refer now to paths relative
to TRIQS python library path. For example,
`import vaspio`
is replaced with
`import applications.dft.converters.plovasp.vasio`
In this way all tests can be executed wtih `build_pytriqs` provided
that the package is installed (the same practice as with other
'dft_tools' tests).
Also, the underscore can now be removed from subdirectory names
because there is no more conflict with module names.
