Need a way to use the development version of CKEditor in SDK

[AnnaTomanek]

At the moment the ckeditor submodule tracks the ckeditor-releases repository. This is fine for working with features that have already been released.

We need a way to make it possible to work with development versions of CKEditor (both master and major branches) in order to be able to easily create samples for new features which have not been released yet.

[Reinmar]

I think that the path to CKEditor directory should be configurable. For SDK development purposes the ckeditor-dev repo should be plugged as the submodule, but when building the SDK one should always specify the path to CKEditor package (e.g. to an external ckeditor-releases repo or to a specific build inside ckeditor-presets directory). The only problem is with the 3rd party plugins such as WSC and SCAYT which would not be testable in dev version of the SDK.

[wwalc]

Seems reasonable in terms of effort required to go this way.

[wwalc]

See also #51.

[AnnaTomanek]

Additional note: We also need a way to select the correct preset, because SDK uses standard-all and the development version creates a really crowded toolbar. This makes it difficult to e.g. take screenshots from the samples for the documentation, addon pages and marketing materials that we create at the same time.