Provide Helper Methods for parsing Map<String,Object> configurations

This issue tracks improvements to the EnhancementEngineHelper implemented as part of STANBOL-488 (EnhancementProperties) and STANBOL-1334, STANBOL-1334 (DereferenceEngine) that are also useful for any other EnhancementEngine that requires to parse

• OSGI component configuration (using Dictionary<String,Object>)
• Enhancement properties (using Map<String, Object>).

The EnhancementEngineHelper will be extended by the following type of static utility methods

    + parseConfigValues(Object value, Class<T> type) : Collection<T>
    + parseFistConfigValue(Object value, Class<T> type) : T
    + getConfigValues(Dictionary<String,Object> config, String property, Class<T> type) : Collection<T> 
    + getConfigValues(EnhancementEngine ee, ContentItem ci, 
        Map<String,Object> enhProp, String property, Class<T> type) Collection<T>

All methods will:

• return NULL if NULL is parsed as config value or the parsed configuration does not contain the requested property
• support Arrays and Collections for multiple values.
• support Arrays of primitive types

Additional optional parameters (for all methods)

• `String preserveNullValues`: if null values should be preserved. By default those will get removed.
• `Collection<T> addTo`: Allows to parse the collection to be filled with the configuration values