Merge develop into master

added comments & deleted unused code

Merge branch 'bugfix/required_realsense_xacro_arg'

+ Users may define out-of-range goals intentionally if they want to move any joint to its limit without knowing the joint's calibrated limit for a specific robot

+ issue with gripper not opening due to commanded opening aperture violating gripper joint bounds
+ added documentation
+ discards object candidate points based on the height of object and the height of the volume of interest used for perception (height of the robot's camera)
+ appears to correct issue when surface is against a wall, which seemed to result in the wall being detected as a large object on the surface

URDF meshes are now organized per the robot batch ID and copied into place using the update_meshes script

Apparently, upstream RealSense changes in ROS Melodic broke Stretch URDF creation. More information about the changes can be found using the following information:

+ realsense-ros release: https://github.com/IntelRealSense/realsense-ros/releases/tag/2.2.14
+ Debian package: ros-melodic-realsense2-description/bionic,now 2.2.14-1bionic.20200630.141906
+ relevant commit: f7cd5fced5

The corrected issue has to do with changes to "use_nominal_extrinsics" specified in the D435i xacros in the realsense2_description package.

The current commmit also changes the d435i launch file for Stretch (d435i_basic.launch) so that it no longer performs "initial_reset" by default. "initial_reset" appears to have resulted in long delays and freezing when bringing up the camera on the robot.

An excerpt from Intel's documentation for initial_reset follows:

"initial_reset: On occasions the device was not closed properly and due to firmware issues needs to reset. If set to true, the device will reset prior to usage." from https://github.com/intel-ros/realsense

+ move up or down to contact handles
+ use new stretch_driver custom effort thresholds
+ successful with tool chest drawer, but has 10 second timeouts after each move until contact