Add MCP73833/4

Forked #1632 and fixed all issues.

• Datasheet
• DFN drawing
• MSOP drawing
• Footprint merge request: kicad-footprints!2550 (closed)
• Footprint generator merge request: kicad-footprint-generator!469 (closed)

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All contributions to the kicad library must follow the KiCad library convention

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

• Provide a URL to a datasheet for the symbol(s) you are contributing
• An example screenshot image is very helpful
• Ensure that the associated footprints match the official footprint library
  • A new fitting footprint must be submitted if the library does not yet contain one.
• If there are matching footprint PRs, provide link(s) as appropriate
• Check the output of the Travis automated check scripts - fix any errors as required
• Give a reason behind any intentional library convention rule violation.