data file format for the plate motion models and boundaries

[yunjunz]

Even though the current version of pypmm and mintpy use a simple and consistent file format for both the plate boundaries in GMT lola format and Euler poles parameters in pure Python files, I think it's more tracable and maintainable if we switch back to their original format downloaded from each of their sources. We could add necessary changes while reading them in the code. Although it is slightly more complicated in our code side, it's easier for a new comer to understand how we get here from the sources that they know of.

[yunjunz]

These data files can be packed together in the code while we redistribute the package in conda-forge or PyPI.