sidereal.py: Internal maintenance specification

This compiled regular expression matches a floating-point number: one or more digits, followed optionally by a decimal point and zero or more digits.

FLOAT_PAT  =  re.compile (
    r'\d+'          # Matches one or more digits
    r'('            # Start optional fraction
      r'[.]'          # Matches the decimal point
      r'\d+'          # Matches one or more digits
    r')?' )          # End optional group