Change units on graphs

nmhydro[CodePlex]
The prerequisite for this feature is implementing feature 8377 (Add support for unit conversion). This feature should be implemented as a quotChange Unitsquot ribbon button in the Graph tab. When the user clicks quotChange Unitsquot a new form
is displayed. This form shows the list of all current variables. For each variable, it shows the current unit and a quotnew unitquot drop down. The quotnew unitquot drop down is populated with all units to which the current unit can be converted. For
example if the current unit is meter then the list contains values such as millimeter, centimeter, kilometer, inch, foot, yard, mile..

When the user selects one of the options, the graphs for the selected variable are re-drawn using the new units and any future graphs of series with the selected variable will also be displayed using the selected units.

[Reported originally by Stephen]

Start by reviewing prerequisite feature 8377 and the Graph tab entry point. Identify how current variables and units are represented, then define the Change Units form and verify that selected conversions redraw existing graphs and apply to future graphs.

Written by the indexing model from the issue text.