Overhauled the tracker system (#172)

* Overhauled the tracker system
Separated the logging and saving capabilities
Changed creation to be consistent and initializing behavior to be defined by a class initializer instead of in the training script
Added class separation between different types of loaders and savers to make the system more verbose

* Changed the saver system to only save the checkpoint once

* Added better error handling for saving checkpoints

* Fixed an error where wandb would error when passed arbitrary kwargs

* Fixed variable naming issues for improved saver
Added more logging during long pauses

* Fixed which methods need to be dummy to immediatly return
Added the ability to set whether you find unused parameters

* Added more logging for when a wandb loader fails

dalle2_pytorch/utils.py

@@ -1,6 +1,11 @@
 import time
 import importlib
 
+# helper functions
+
+def exists(val):
+    return val is not None
+
 # time helpers
 
 class Timer: