Bug 197228 Need updaet createdBy info when serialize the module
When open module, designer will pass the property map which contains the createdBy info. this info should be retained by moduleHandle and then be updated and written when doing serialization. Note if this info is null, model should not update it during serialization. This could happen for api users or third-party designer. For BIRT designer, it will guarantee this value always not null.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/core/Module.java
{
		this.signature = signature;
	}
	/**
	 * Gets the UTF signature of this module file.
	 * 
	 * @return the UTF signature of the module file.
	 */
	public String getUTFSignature( )
	{
		return signature;
	}
	/**
	 * Returns the number of slots of the module. For the library and the report
	 * design, this number is different.
	 * 
	 * @return the number of slots of the module
	 */
	protected abstract int getSlotCount( );
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.birt.report.model.core.DesignElement#getSlot(int)
	 */
	public ContainerSlot getSlot( int slot )
	{
		assert slot >= 0 && slot < getSlotCount( );
		return slots[slot];
	}
	/**