Update xacro model files for syntax update and conversion script to standalone tools

(cherry picked from commit 996579870e034d4ba7ae020a086964fd28593e32)
Change names in robot model to be more descriptive and follow conventions

(cherry picked from commit 27359e3d80faca04d6fbc8293642b252a1968ed8)
Add an arm mocking launch file and some manual commandline hints

(cherry picked from commit 185ccc3e9c189d8dbf9fb628fb17a56ce9060f94)
Update README.md with branch information