Basic SPEF syntax highlighting

Very basic SPEF (Standard Parasitic Exchange Format IEEE 1481-2009) syntax highlighting only (i.e., not full language support) for detailed nets (D_NET). May incidentally support reduced nets (R_NET) since the syntax is fairly similar.

Includes coloring for

• Headers (e.g., *SPEF, *DESIGN, etc.)
  • Design flow substrings (e.g., "PIN_CAP NONE", "NAME_SCOPE LOCAL", etc.)
• Units (e.g., *T_UNIT, NS, FF, etc.)
• Comments
• Name mapped items
• Basic keywords (*D_NET, *I lines, *P lines, *N lines)
• Subnodes and pins
• Instance names as separate entites from numbers
• Numbers including floats