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>