lazy imports in lib5c toolbox

[Thomas Gilgenast]

the lib5c command line toolbox should use lazy imports

currently, it imports the entire tree every time

this causes simple tasks like printing the help message with lib5c -h to take way too long

this can be fixed by lazily importing packages only when they are specified by the particular lib5c subcommand invoked

[Thomas Gilgenast]

lazy-import non-parser modules in lib5c toolbox

fixes #1

→ <<cset e0994bdcfb25>>