Make initilization a more seamless process

[hak33m16]

• Currently, you have to explicitly run gpm init before you can use the CLI. Since we're already having to check whether we're initialized or not, when any gpm command is run for the first time, we should prompt for initialization
• Since people may be prompted unexpectedly when trying to use gpm for the first time, we should revamp the initialization function to be more robust, and account for seamlessly guiding users out of a state where gpm may be partially initialized