fix issue where tool does not work with firebase-tools v15

[amalej]

fixes #66

firebase-tools v15 will introduce a lazy loading of commands feature. this will cause commands to not be all loaded on default. so we need to manually load them. Used the ff logic to do it

1. Get the client object tree
2. Determine which "branch" of the object tree are commands(the ones with load function)
3. Store all those commands in a list
4. run getCommand(command) for each command to register/load them
5. get the client after loading all the commands