Move TinyMCE into a separate module

[121GWJolt]

TinyMCE currently requires a license to host it on anything other than an LGPLv3-compatible use case. Therefore, its inclusion in anything without the expensive self-hosting license has a legal risk attached to it. Potential alternatives include Trumbowyg and Summernote, both of which are MIT-licensed.

[tidyui]

I have created a feature-branch for this and started working on it:

https://github.com/PiranhaCMS/piranha.core/tree/features/editor-restructuring

I have moved TinyMCE from the manager into its own package and also added a package for Summernote as an example. It's not complete, but I have added basic image library integration for the Summernote editor. The example MvcWeb uses the TinyMCE package and the RazorWeb example uses the Summernote package

[121GWJolt]

Editor loads and I like the interface a lot. Media plugin loads for me too.

For saving I propose possibly hooking into this function or this function and changing the signature of the addInline method to have a callback for saving the model posted to it. Callback could pass one parameter containing the string value of Summernote's contents.

[tidyui]

I have gone through licensing terms and taken precautions. What this means is that I've added the correct "Powered by Tiny" link on all editors when active. As fas as LGPL this license does not prohibit usage in closed commercial software at all when components are used as a library. The only thing LGPL tries to control is that if you make changes or modifications to the library, these changes are also to be considered LGPL.

I am 100% sure that it's not a problem using LGPL components in closed source software as we in fact used this license for the old legacy version of Piranha for many years before switching to MIT.