Some minor fixes

[tu500]

First, I really like this software for creating population guides. Thanks!

I have found some minor usage and rendering bugs and wrote some patches. I don't know if these are the 'right' solutions, especially for the remapping fix, as that passes around implicit state.

Also from a new user perspective I have some remarks about missing documentation for a v1 release. Maybe these should go into an own issue, but for now:

• --show-lib-paths should probably work without having to specify valid input files but this needs some work
• a better explanation about the populate source file header, specifically the distinction between params and the other options (maybe rename params to plot_params?) and which options go where

[yaqwsx]

I am sorry that it took me so long to review these changes! Thank you for them.

The --show-lib-paths should be probably extracted into a separate command.

[tu500]

Not a problem, thanks for the work.