Adding conventional PID computation
Merging changes from other branch
Fixing documentation
adding doxygen deprecation flags
Cleaning up documentation, making argument names in function declaration match those in the implementation
Make public getControllerByName method thread-safe.

Existing virtual non-threadsafe method has been suffixed with -Impl and pushed
to protected class scope. In-class uses call getControllerByNameImpl, as the
lock has already been acquired.
Merge pull request #12 from jbohren-forks/feature-conventional-pid-error-sign

Adding conventional PID computation, deprecating current PID computation
Merge pull request #15 from pal-robotics/master

Make public getControllerByName method thread-safe.