simplify sources jarring config

I think <phase>verify</phase> is the default
small refactoring
create ConfigReader

(initial structure for system properties interpolation)
add system property interpolation to ConfigReader
split datasource creation / destruction logic out

make a new DatasourceManager class that is responsible for creating or looking up the
maintenance datasource, depending on configuration parameters
organize imports
make H2 dependency optional
remove pool reference when the pool is disposed
add a note about Tomcat memory leak warnings
Merge pull request #3 from CruGlobal/add-system-property-config-support

Add system property config support