Clean Install Libraries

[wraybowling]

I've noticed that while messing around with the platformio.ini file, especially when adding and removing dependencies, they are not necessarily cleaned up. Once the text of a library has been deleted from the text file, the GUI assumes that the library was uninstalled but that is not the case until the lib is actually removed from the .pio folder. This can lead to hours of confusion while a library is still in place when I think that it is not. I think a "clean install libraries" would be useful, akin to the "clean install" on npm where all libraries are removed, redownloaded, and re-installed based on what the configuration says is correct.

[ivankravets]

Duplicate of platformio/platformio-core#3076