Support passing language info to drag and drop setup

- Deriving langInfo moved out of createLayout() and setup initially once-and-for-all and included in layoutInfo to be used e.g. when setting up drag and drop event
- Fixed bug causing en-US lang to be (permanently) overridden by lang set in options. Use jQuery extend deep copy when setting up langInfo to ensure that English text is used if no text is given the the specified lang.
Update Danish language file
Updated dist files
Fixed typo
Minor fixes to satisfy jshint
Fix merging local language

- English language file should not be overridden
- Deep merge
Merge pull request #708 from AgileLeanWorks/bug/fix_language_merge

Fix merging local language
Improve English, move changelog to separate file, add features
Merge pull request #714 from dandv/develop

Improve English, move changelog to separate file, add features
Merge branch 'feature/drag_drop_lang' of github.com:AgileLeanWorks/summernote into AgileLeanWorks-feature/drag_drop_lang

Conflicts:
	dist/summernote.js
	dist/summernote.min.js
	src/js/Renderer.js
Merge branch 'AgileLeanWorks-feature/drag_drop_lang' into develop
refactor: rename elHolder to holder.