pom.xml: make h2 the default profile

Signed-off-by: Pierre-Alexandre Meyer <pierre@mouraf.org>
pom.xml: introduce embeddeddb sub-modules

Signed-off-by: Pierre-Alexandre Meyer <pierre@mouraf.org>
pom.xml: change default test behavior

By default, only fast tests are run now. Use the h2 profile to run
slow tests on H2 and the mysql profile to run them on MySQL.

Travis will now run slow tests (on H2) as well.

Signed-off-by: Pierre-Alexandre Meyer <pierre@mouraf.org>
pom.xml: upgrade testng to 6.8.8

I am currently debugging weird behaviors when slow tests fail
in killbill-beatrix. We were on a very old version of TestNG, hoping
the upgrade will help.

Signed-off-by: Pierre-Alexandre Meyer <pierre@mouraf.org>