* 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.

docs/source/diagram-code/ucloud

@@ -0,0 +1,44 @@
+graph LR
+    style ucloud fill:#FFD2FC
+    style cron fill:#FFF696
+    style infrastructure fill:#BDF0FF
+    subgraph ucloud[ucloud]
+        ucloud-cli[CLI]-->ucloud-api[API]
+        ucloud-api-->ucloud-scheduler[Scheduler]
+        ucloud-api-->ucloud-imagescanner[Image Scanner]
+        ucloud-api-->ucloud-host[Host]
+        ucloud-scheduler-->ucloud-host
+
+        ucloud-host-->need-networking{VM need Networking}
+        need-networking-->|Yes| networking-scripts
+        need-networking-->|No| VM[Virtual Machine]
+        need-networking-->|SLAAC?| radvd
+        networking-scripts-->VM
+        networking-scripts--Create Networks Devices-->networking-scripts
+        subgraph cron[Cron Jobs]
+            ucloud-imagescanner
+            ucloud-filescanner[File Scanner]
+            ucloud-filescanner--Track User files-->ucloud-filescanner
+        end
+ subgraph infrastructure[Infrastructure]
+    radvd
+    etcd
+    networking-scripts[Networking Scripts]
+    ucloud-imagescanner-->image-store
+    image-store{Image Store}
+    image-store-->|CEPH| ceph
+    image-store-->|FILE| file-system
+    ceph[CEPH]
+    file-system[File System]
+    end
+subgraph virtual-machine[Virtual Machine]
+  VM
+  VM-->ucloud-init
+
+end
+
+subgraph metadata-group[Metadata Server]
+metadata-->ucloud-init
+ucloud-init<-->metadata
+end
+end