Add test linuxbuild (build Linux kernel)

Signed-off-by: Ruda Moura <rmoura@redhat.com>
Merge pull request #103 from lmr/test-subprocess-improvements

Test subprocess improvements
Merge pull request #102 from ruda/kernel-build

Add test linuxbuild (build Linux kernel)
avocado: Create sysinfo in more points of the job execution

Take system info in more opportunities:

1) Start job
2) End job
3) Start test
4) End test

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
docs: Add Results Specification

That explains the dir structure for avocado test results.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>