Add ability to close FlowManager without reset database

[carmas123]

DBFlow Version: 4.10
Issue Kind (Bug, Question, Feature): Feature

Before all, thank you so much for your big release (4.10).

Description:
I need to have a static method into FlowManager that deinitialize the FlowManager to be reinitialized with init() method.
We can have a method like this into "FlowManager.java":

    /**
     * Close reference to context and {@link FlowConfig}
     */
    public static synchronized void close() {
        Set<Map.Entry<Class<?>, DatabaseDefinition>> entrySet =
            globalDatabaseHolder.databaseClassLookupMap.entrySet();
        for (Map.Entry<Class<?>, DatabaseDefinition> value : entrySet) {
            value.getValue().close();
        }

        config = null;

        // Reset the global database holder.
        globalDatabaseHolder = new GlobalDatabaseHolder();
        loadedModules.clear();
    }

My best regards.

[baranowskinet]

I also has the same problem and for now I have work around by pass flag to application method:
@OverRide
public boolean deleteDatabase(String name) {...}
to prevent delete db.

As I mentioned in another post better will be to have it per individual database (by class or even better by db name).

[agrosner]

added method for 4.1.2 in develop now.