Bug 183918 get relative file path of linkage library
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/LibraryHandle.java
import org.eclipse.birt.report.model.elements.Theme;
import org.eclipse.birt.report.model.elements.interfaces.ILibraryModel;
import org.eclipse.birt.report.model.elements.interfaces.IThemeModel;
import org.eclipse.birt.report.model.i18n.ModelMessages;
import org.eclipse.birt.report.model.util.ModelUtil;
/**
 * Represents the handle of library element. The library contains the resuable
 * element components.
 * 
 * <table border="1" cellpadding="2" cellspacing="2" style="border-collapse:
 * collapse" bordercolor="#111111">
 * <th width="20%">Content Item</th>
 * <th width="40%">Description</th>
 * 
 * <tr>
 * <td>Code Modules</td>
 * <td>Global scripts that apply to the report as a whole.</td>
 * </tr>
 * 
 * <tr>
 * <td>Parameters</td>
 * <td>A list of Parameter elements that describe the data that the user can
 * enter when running the report.</td>
 * </tr>
 * 
 * <tr>
 * <td>Data Sources</td>
 * <td>The connections used by the report.</td>
 * </tr>
 *