Split off pnid variables from main theme

[LuPro]

Currently the space team theme contains a lot of variable declarations that are completely useless for most projects but are used in the web_ecui/pnid project (where the theme originates from). I'd like to split this off from the ST theme by providing a "load plugin" infrastructure or the like. this way I could put the variable declarations for the pnid as a separate .css into the pnid directory and on theme init add these .css files to their respective themes so switching between light/dark/other also swaps out these "plugin" css files.