Add section describing how OIE is expected to be compatible with Mirth and other forks

Signed-off-by: Jon Bartels <jonathan.bartels@gmail.com>

Author: jonbartels

README.md

@@ -39,6 +39,19 @@ Please do your best to include the following information in your issue:
 * The output of the command you executed (Hint: add `--progress=plain` to your `docker` command to see the full output)
 * Use [Markdown](https://guides.github.com/features/mastering-markdown/) to format your issue text, ESPECIALLY if you are including code snippets or command output. This will make it easier for us to read and understand your issue.
 
+#### Compatibility with Mirth Connect, NextGen Connect, BridgeLink, and other Mirth forks
+
+Open Integration Engine is a direct fork from Mirth Connect 4.5.2. You will be able to export channels, codes, and other resources from Mirth Connect and import them into Open Integration Engine without any issues. The same applies to NextGen Connect, BridgeLink, and other Mirth forks that are based on Mirth Connect 4.5.2 or earlier.
+
+When upgradging to Open Integration Engine from Mirth Connect, NextGen Connect, or BridgeLink, you should:
+* Backup your Mirth Connect database and configuration files.
+* Export channels, code templates, and other resources from Mirth Connect. The server backup feature in Mirth Connect can be used to export all channels and resources.
+* Compare `mirth.properties` between Mirth Connect and Open Integration Engine. Apply your customizations of Mirth Connect to the Open Integration Engine `mirth.properties` file.
+* Start Open Integration Engine 
+* Import the channels, code templates, and other resources you exported from Mirth Connect into Open Integration Engine. We suggest doing this one by one. The Server backup is epxected to work but going piece-by-piece will allow you to catch any issues that may arise during the import process.
+
+Open Integration Engine is currently compatible with Mirth Connect 4.5.2 and earlier versions. Since Mirth Connect 4.6.0 and later are closed-source, Open Integration Engine is not compatible with those versions. If you are using Mirth Connect 4.6.0 or later, you will need to migrate your channels and resources to Open Integration Engine manually. BridgeLink and other Mirth forks are generally expected to be compatible, however Open Integration Engine does not have a formal compatibility matrix with these forks. 
+
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 <a name="what-is-oie"></a>