Allow NaN as an initial value for double Shared variables

[Enrico_Segre]

This would be useful for variables whose value is not yet available at deployment time, and is filled later by some process.

Currently (LV2017.1f3), it is not even possible to input a non-numeric value in the inital value page in the variable editor. Attempting to do it programmatically like this:

produces a LabVIEW:  (Hex 0x8BBB0018) Invalid float value.

Whereas, blindly editing the lvlib file to 

<Property Name="Initial Value:Value" Type="Str">NaN</Property>

produces a "deployment failed (error: -1950678996, LabVIEW:  The variable configuration is invalid.  Edit the variable properties to correct the configuration.)." at deploy time.

[Darren]

Moved to CAR database: CAR 720385