Bug 152828 Add the projectFolder property on module
When user doesn't set the resource folder path in designer, there should be a default working path for Birt to manage the report design and find the related resources. A new property should be added on Module: name: projectFolder type:URL This property only can be given from the open design method from session but should not be set after the module initialized. Concern about the backward compatiblity issue, a new method will be added. Open design with a config argument.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/SessionHandle.java
* <ul>
	 * <li><code>UNITS_IN</code></li>
	 * <li><code>UNITS_CM</code></li>
	 * <li><code>UNITS_MM</code></li>
	 * <li><code>UNITS_PT</code></li>
	 * <li><code>UNITS_PC</code></li>
	 * </ul>
	 * 
	 * @param units
	 *            the units to set for the session -- application
	 * @throws PropertyValueException
	 *             if <code>units</code> is not one of the above
	 * 
	 * @see org.eclipse.birt.report.model.api.metadata.DimensionValue
	 */
	public void setApplicationUnits( String units )
			throws PropertyValueException
	{
		session.setUnits( units );
	}
	/**
	 * Returns the current session (application) units. The return values are
	 * defined in <code>DesignChoiceConstants</code> and is one of:
	 * 
	 * <ul>
	 * <li><code>UNITS_IN</code></li>
	 * <li><code>UNITS_CM</code></li>
	 * <li><code>UNITS_MM</code></li>
	 * <li><code>UNITS_PT</code></li>
	 * <li><code>UNITS_PC</code></li>