Create a TangoAttr hardware

This MR provides a TangoAttr hardware device in order to easy tune beamlines.

• !349 (merged) have to be merged first

For monitoring purpose, people usually care about few things. Such simplified concept (basically the same thing as Taurus) can became really useful to provide something useful at low cost, especially if a Tango device is not yet properly supported.

  - name: lima nb frames
    id: lima_simulator__acq_nb_frames
    url: tango:///id00/limaccds/simulator1/acq_nb_frames

And few information are provided like

• State of the device state, status
• State of the attribute value, quality, data_type, name...
• Config of the attribute format, display_unit, label, description...

From this bunch of information it's easy to create a generic widget.

Proposal

There is way to generalize this concept, but it's probably not the good time to do that. Cause it is not a so easy task, and there is more important things to do.

• Instead of tangoattr the abstract object could be named quantity
  • so what it could be mapped by many more stuffs
• This object could provide both normalized fields and extra fields
  • normalized: dtype, shape
  • tango specific: tangoFormat