Introduce IR compiler

[marvinbuff]

For a project we are working on I depend on a feature of the new IR compiler. For that reason we need to have this fork which support IR. And as we have already done this work and you have a related issue #37 , we thought we would create a draft PR to share the progress we made with you. From our side this is done, so if you don't want to merge it you can just close it. Otherwise, we can try to make it mergeable together. Let me know what is best for you.

Unsolved Issues

• The compiler is set to IR and not BOTH, this would be a breaking change for all users and is obviously not acceptable. However, there is a issue with the artefacts if BOTH is used. As I am not efficient in Gradle setups I didn't fix it and just went with IR.
• There are clear issues with styling of the test-app. One instance is that the cushion underneath the app bar does not work anymore and all content is shoved upwards. I did not investigate if there are other issues and just fixed that there are no errors thrown.
• The hot-reloading fails.

Solved Issues

• Added external keyword to all interfaces implementing RProps.
• Added @jsExport annotation for all classes implementing RState, or converted them to interfaces where possible.
• Fixed weird naming clash when importing javascript modules.
• Fixed the Spacing class.
• Replaced usage of div with custom javascript style to styledDiv as it caused errors.

Added functionality (which could be merged in another PR if this one is discarded)

• Changed paged map to Enum for convenience

Comments

• I did not have to add @JsExport to classes implementing RComponent, contrary to the suggestion in this change Intellij warns me to do so.
• I think a next step should be to update Kotlin and the wrappers as there could already be changes to the behaviour I encountered.

[cfnz]

I have added a new branch - IR-Compiler and edited this pull request to target that branch. Maybe we track this along there and once the IR compiler is out of Alpha (or Beta) we look at merging. I know there is talk of making the IR Compiler not require some of the extra things it now requires, so some of this work may eventually be not required.