adds the THAT1512 chip to the audio amp library

Created by: krinkleneck

Adding the THAT Corp. THAT1512 Audio Amplifier Package. Default assignment is DIP-8, but it comes in multiple package types.

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Thanks for reading a pull request to contribute to the KiCad libraries! To speed up integration of your PR, please check the following items:

• http://www.thatcorp.com/datashts/THAT_1510-1512_Datasheet.pdf

• Packages DIP & SOIC

• [?] Is the lack of color a violation of conventions?