[Sendportal] Visual e-mail builder

First off: thanks for all your efforts that already went into sendportal. I've recently did the installation and I'm impressed, the interface is so clean and easy to use. Thumbs up! The thing I was wondering is whether or not there are future plans to add a visual e-mail builder to the project. As far as I can tell, right now you have a template (containing a header/footer) and the `{{content}}` is injected from within the campaign. Having the wysiwyg editor is a good start, but how cool would it be if you were able to drag-and-drop building blocks in the editor and create a campaign that way? There are a few (good) open-source projects available for these features and a as far as I can see it doesn't have to be a breaking change since this builder could be optional depending on the template type (`basic` for a wysiwyg content field or `builder` if the template contains one or more blocks). I'd definitely be willing to invest some of my time into figuring out the options and w