Rearrange files and minor updates

* Move nav2_tree_nodes.xml and groot instruction to nav2_beahvior_tree

* Run cmake install rules for nav2_tree_nodes.xml

Signed-off-by: Sarathkrishnan Ramesh <sarathkrishnan99@gmail.com>

Author: Sarath18

nav2_behavior_tree/CMakeLists.txt

@@ -120,6 +120,8 @@ install(DIRECTORY include/
   DESTINATION include/
 )
 
+install(FILES nav2_tree_nodes.xml DESTINATION share/${PROJECT_NAME})
+
 if(BUILD_TESTING)
   find_package(ament_lint_auto REQUIRED)
   ament_lint_auto_find_test_dependencies()

nav2_bt_navigator/behavior_trees/README.md renamed to nav2_behavior_tree/groot_instructions.md

@@ -1,12 +1,12 @@
 # Instructions on using Groot
 [Groot](https://github.com/BehaviorTree/Groot) is the companion application of [BehaviorTree.CPP](https://github.com/BehaviorTree/BehaviorTree.CPP) to create, edit, and monitor behavior trees.
 
-##### Note: Currently only supports visualization of the behavior tree along with the creation of new nodes (except ControlNodes) using the Groot. Additional features under development.
+##### Note: Currently fully supports visualization of the behavior trees. It also supports the creation of custom nodes except control flow nodes. Support for custom control flow nodes and real-time monitoring is under development.
 
 ### BehaviorTree visualization
 To visualize the behavior trees using Groot:
 1. Open Groot in editor mode
 2. Select the `Load palette from file` option  (import button) near the top left corner.
-3. Open the file `/path/to/navigation2/nav2_bt_navigator/behavior_trees/nav2_tree_nodes.xml` to import all the behavior tree nodes used for navigation.
+3. Open the file `/path/to/navigation2/nav2_behavior_tree/nav2_tree_nodes.xml` to import all the behavior tree nodes used for navigation.
 4. Select `Load tree` option near the top left corner
 5. Browse the tree you want to visualize the select ok.

nav2_bt_navigator/behavior_trees/nav2_tree_nodes.xml renamed to nav2_behavior_tree/nav2_tree_nodes.xml

@@ -1,3 +1,9 @@
+<?xml version="1.0"?>
+<!--
+  For instructions on using Groot and description of the following BehaviorTree nodes,
+  please refer to the groot_instructions.md and REAMDE.md respectively located in the 
+  nav2_behavior_tree package.
+-->
 <root>
   <TreeNodesModel>
     <!-- ############################### ACTION NODES ################################# -->