Solar interpolation macro

[dguittet]

Description

Fixes #1777

The problem was that the code was always assuming the Hour value was reported at bottom of the hour, and not checking if it was bottom of the hour or top of the hour.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update
• This change modifies variables in existing compute modules. Please see Checking for PySAM Incompatible API Changes.
• This change requires updating the PySAM files via export_config. Please see When do the PySAM files need to be regenerated?