Improve tests and change tests/ directory layout

Add run-report.py and test_list.py files which are an extended test framework
providing memory and CPU sampling of the session daemon during the tests.

Tests are now divided on a per package basis. The kernel/ directory contains
integration tests for lttng-modules (kernel tracer). ust/ directory contains
tests for lttng-ust and tools/ directory has the unit tests of lttng-tools
itself which does not test tracer integration.

First patch aimed at improving test coverage of the lttng 2.0 toolchain and
provide the python framework for more detailled analysis.

Use make check to run them all or use run-report.py and select which tests to
run in test_list.py.

Signed-off-by: David Goulet <dgoulet@efficios.com>