Tree component addition, documentation update

src/main/java/com/googlecode/lanterna/graphics/AbstractTheme.java

@@ -284,6 +284,20 @@ public boolean isCursorVisible() {
             return cursorVisible;
         }
 
+        @Override
+        public int getIntegerProperty(String name, int defaultValue) {
+            String propertyValue = node.propertyMap.get(name);
+            if(propertyValue == null) {
+                if(node == rootNode) {
+                    return defaultValue;
+                }
+                else {
+                    return new DefinitionImpl(node.parent).getIntegerProperty(name, defaultValue);
+                }
+            }
+            return Integer.parseInt(propertyValue);
+        }
+
         @Override
         public boolean getBooleanProperty(String name, boolean defaultValue) {
             String propertyValue = node.propertyMap.get(name);

src/main/java/com/googlecode/lanterna/graphics/DelegatingThemeDefinition.java

@@ -76,6 +76,11 @@ public ThemeStyle getCustom(String name, ThemeStyle defaultValue) {
         return themeDefinition.getCustom(name, defaultValue);
     }
 
+    @Override
+    public int getIntegerProperty(String name, int defaultValue) {
+        return themeDefinition.getIntegerProperty(name, defaultValue);
+    }
+
     @Override
     public boolean getBooleanProperty(String name, boolean defaultValue) {
         return themeDefinition.getBooleanProperty(name, defaultValue);

src/main/java/com/googlecode/lanterna/graphics/SimpleTheme.java

@@ -319,6 +319,15 @@ public synchronized Definition setCustom(String name, TextColor foreground, Text
             return this;
         }
 
+        public synchronized int getIntegerProperty(String name, int defaultValue) {
+            return Integer.parseInt(properties.getProperty(name, Integer.toString(defaultValue)));
+        }
+
+        public synchronized Definition setIntegerProperty(String name, int value) {
+            properties.setProperty(name, Integer.toString(value));
+            return this;
+        }
+
         @Override
         public synchronized boolean getBooleanProperty(String name, boolean defaultValue) {
             return Boolean.parseBoolean(properties.getProperty(name, Boolean.toString(defaultValue)));

src/main/java/com/googlecode/lanterna/graphics/ThemeDefinition.java

@@ -89,6 +89,15 @@ public interface ThemeDefinition {
      */
     boolean getBooleanProperty(String name, boolean defaultValue);
 
+    /**
+     * Retrieves a custom integer property, if one is available by this name. Will return a supplied default value if
+     * no such property could be found within this {@link ThemeDefinition}.
+     * @param name Name of the integer property to look up
+     * @param defaultValue What to return if the there is no property with this name
+     * @return The property value stored in this theme definition, parsed as a integer
+     */
+    int getIntegerProperty(String name, int defaultValue);
+
     /**
      * Asks the theme definition for this component if the theme thinks that the text cursor should be visible or not.
      * Note that certain components might have a visible state depending on the context and the current data set, in