Jinja2 template engine for URDF files

[johnwason]

Currently xacro is used to parameterize and generate URDF files. Xacro has quite a few limitations, including the lack of a C++ library. Jinja2 is the de-facto Python template engine,. It was originally intended to be used to render HTML web pages, but is being used in more places. For example, conda uses Jinja2 with its configuration files to add an additional layer of customization. There appears to be a C++ implementation of the Jinja2 template engine: https://github.com/jinja2cpp/Jinja2Cpp . I think it would be interesting to see if we can use Jinja2 with the URDF and SRDF inputs to Tesseract.