Migrate from V1 to V2 Guide (#678)

* Add V1 to V1 migration guide

* Polish the migration guide document

* Fix md extra characters

* Fix formatting

* fix local references

* Fix code snippet

* remove unique from code

* client id as parameter

* fix variables

* Fix

* Fix

* remove new lines from code snippet

* Apply reviews

* excape apostrophes

* Remove apostrophe escapes

* fix some typos

* shorten code lines

* Remove apostrophe

* Fix typo

* Fix wording

* Try different local link format

* Fix remaining local link - remove ++

* Fix NOTE tags

* apply various fixes

* Sync with the Java migration guide

* add comments to job lambdas

* Fix quoted links

* Fix capitalization

* fix typo and table

* Remove extra lines

* more fixes

* fix

* fix comments

Author: alfred2g

README.md

@@ -10,6 +10,7 @@ __Jump To:__
 * [FAQ](./documents/FAQ.md)
 * [API Docs](https://aws.github.io/aws-iot-device-sdk-cpp-v2/)
 * [MQTT5 User Guide](./documents/MQTT5_Userguide.md)
+* [Migration Guide from the AWS IoT SDK for C++ v1](./documents/MIGRATION_GUIDE.md)
 
 
 ## Installation