Add settings to make Spinitron data primary source

[Pythagory]

Presently, descriptions for shows and DJs are not updated on subsequent imports from Spinitron. We should add the option to have descriptions update on import, as some users are taking advantage of custom images without wanting to set custom descriptions.

[mtomcal]

Added the updating existing show descriptions option 0520dc3cd5689c719cd10e13fb050b106ed24ee4