* Refactoring

* Fix issue that causes a new image store to be created at every start of ucloud-api.
* VM Migration API call now takes hostname instead of host key.
* StorageHandler Classes are introduced. They transparently handles things related to importing of image, make vm out of image, resize vm image, delete vm image etc.
* Loggers added to __init__.py of every ucloud component's subpackage.
* Non-Trivial Timeout Events are no longer logged.
* Fix issue that prevents removal of stopped VMs (i.e VMs that are successfully migrated).
* Improved unit handling added. e.g MB, Mb, mB, mb are all Mega Bytes.
* VM migration is now possible on IPv6 host.
* Destination VM (receiving side of migration of a vm) now correctly expects incoming data on free ephemeral port.
* Traceback is no longer output to screen, instead it goes to log file.
* All sanity checks are put into a single file. These checks are run by ucloud.py before running any of ucloud component.

common/classes.py

@@ -1,28 +1,6 @@
-from decouple import Config, RepositoryEnv, UndefinedValueError
 from etcd3_wrapper import EtcdEntry
 
 
-class EnvironmentVariables:
-    def __init__(self, env_file):
-        try:
-            env_config = Config(RepositoryEnv(env_file))
-        except FileNotFoundError:
-            print("{} does not exists".format(env_file))
-            exit(1)
-        else:
-            self.config = env_config
-
-    def get(self, *args, **kwargs):
-        """Return value of var from env_vars"""
-        try:
-            value = self.config.get(*args, **kwargs)
-        except UndefinedValueError as e:
-            print(e)
-            exit(1)
-        else:
-            return value
-
-
 class SpecificEtcdEntryBase:
     def __init__(self, e: EtcdEntry):
         self.key = e.key