add warning for RDI in Beam coordinates

[ocehugo]

Problem reported by Shawn Meredyk.

There is no clue to the user, within the toolbox app, that we only accept RDI adcp in ENU coordinates. Files in Beam coordinates may be silently processed without any warning to the user and may lead to the thinking the data was bin mapped when it wasn't.

The problem lies that workhorseParser forces all variables to be associated with HEIGHT_ABOVE_SENSOR, without verification. The comment may also be misleading without proper verification of the coordinates. Although the current behaviour is consistent with the wiki (the parser assume RDI is coming in ENU), we may need to block non-ENU coordinates to avoid confusion.

Requirements:

• Check storage of ENU/BEAM metadata from instrument.
• Handle/Avoid non-ENU coordinates.
• Create correct warnings.
• evaluate this in face of new code in 675 rebase #683