Made modifications to the RigidBody(2D) descriptions.

(cherry picked from commit 50e6b3c005)

doc/classes/RigidBody.xml

@@ -5,10 +5,9 @@
 	</brief_description>
 	<description>
 		This is the node that implements full 3D physics. This means that you do not control a RigidBody directly. Instead you can apply forces to it (gravity, impulses, etc.), and the physics simulation will calculate the resulting movement, collision, bouncing, rotating, etc.
-		This node can use custom force integration, for writing complex physics motion behavior per node.
+		A RigidBody has 4 behavior [member mode]s: Rigid, Static, Character, and Kinematic.
-		This node can shift state between regular Rigid body, Kinematic, Character or Static.
+		[b]Note:[/b] Don't change a RigidBody's position every frame or very often. Sporadic changes work fine, but physics runs at a different granularity (fixed hz) than usual rendering (process callback) and maybe even in a separate thread, so changing this from a process loop will yield strange behavior. If you need to directly affect the body's state, use [method _integrate_forces], which allows you to directly access the physics state.
-		Character mode forbids this node from being rotated.
+		If you need to override the default physics behavior, you can write a custom force integration. See [member custom_integrator].
-		As a warning, don't change RigidBody's position every frame or very often. Sporadic changes work fine, but physics runs at a different granularity (fixed hz) than usual rendering (process callback) and maybe even in a separate thread, so changing this from a process loop will yield strange behavior.
 	</description>
 	<tutorials>
 		http://docs.godotengine.org/en/3.0/tutorials/physics/physics_introduction.html

doc/classes/RigidBody2D.xml

@@ -5,11 +5,7 @@
 	</brief_description>
 	<description>
 		This node implements simulated 2D physics. You do not control a RigidBody2D directly. Instead you apply forces to it (gravity, impulses, etc.) and the physics simulation calculates the resulting movement based on its mass, friction, and other physical properties.
-		A RigidBody2D has 4 behavior modes (see [member mode]):
+		A RigidBody2D has 4 behavior [member mode]s: Rigid, Static, Character, and Kinematic.
-		- [b]Rigid[/b]: The body behaves as a physical object. It collides with other bodies and responds to forces applied to it. This is the default mode.
-		- [b]Static[/b]: The body behaves like a [StaticBody2D] and does not move.
-		- [b]Character[/b]: Similar to [code]Rigid[/code] mode, but the body can not rotate.
-		- [b]Kinematic[/b]: The body behaves like a [KinematicBody2D], and must be moved by code.
 		[b]Note:[/b] You should not change a RigidBody2D's [code]position[/code] or [code]linear_velocity[/code] every frame or even very often. If you need to directly affect the body's state, use [method _integrate_forces], which allows you to directly access the physics state.
 		If you need to override the default physics behavior, you can write a custom force integration. See [member custom_integrator].
 	</description>