* moved `~/cmd/app.go` to `~/cmd/my5g-RANTester/main.go`
* refactored logging, command declaration
* split into multiple files
* switched to using constants and fmt.Sprintf for formatting stuff

* config global state removed from the config module
* config global state now resides in main, TODO to remove it
* config now creates a default if none are found
* added command line option for specifying the config file
* added command line option to specify the log level
* config directory now looks in user dir, in a platform agnostic way.
ex: on linux, will typically look in `~/.config/my5g/RANTester` for file
`config.yml`
* updated go.mod to use go v1.16
* embedded default config file data
* errors are now bubbled up appropriately
* depends on my5G#33