Functional tests for all databases

For now, functional tests works only for hsqldb database, because:

1. xwiki-enterprise-database create database only for hsqldb
2. xwiki-enterprise create distribution only for hsqldb (src/main/resources/hibernate.cfg.hsql.xml)

I propose small changes to xwiki maven build configuration, what will allow to create distribution for all databases and run functional tests on it. patches is attached.
Databases selected by profile, ex: mvn -Pmysql install

This changes will be useful in integration test system.

This changes may be dangerous for normal users, because xwiki-enterprise-database will damage data in 'xwiki' pgsql/mysql databases on localhost. Maybe we need somehow disable this by default.