Add multiple gopath support for ParsePackagesFromDir.
Improves gloomyzerg@39cc0bc04e109ff0f69e73d567354d9e82b7c24c fix for #332 that got lost on some merge.
This removes the filepath.Walk() when loading configuration,
as it can read a Beefile from another project in the $GOPATH.
Now config.LoadConfig() is called for all available commands.
create sub packages
delete unused code
delete code from not use command cmdRouter,cmdTest, cmdRundocs
make command plugins
check with gosimple,staticcheck,go vet,unused,unconvert
