Technosoft motor support

[gilesknap]

This adds a test that shows an example of a Technosoft motor controller and axes.

It also includes the following fixes to make this work:

• make sure jija renders of args get back into the args list for subsequent arg rendering
• add a 'shared' key to the root of IOC for anchors that can avoid repetition in the Entities
• add a message to show which Jinja template was being rendered when Jinja exceptions occur to aid debugging
• dont raise an exception when using the utils.get_var for not existent argument (easier on debugging and can help with bootstrapping a string concatenation for example)