Adding of features asked for in issue #397

Created by: TSnatch72

More than a year ago i suggested what keymaps to be used for the shortcuts asked in #397 (closed). Maintainer explained what would have to be done in the code to add these to the project, but i preferred to left that to someone else back then because i have almost no knowledge of C++ or programming in general. Since the Issue thread went silent after that, i eventually decided to give it a try and do it myself following the instruction of Shatur. I don't think i knew what i was doing and I'm not sure if i did it right, if i forgot something, if i followed the style of the project or if i broke things rather than improving them, but i hope these commits will at least be helpful in finally adding the features and closing the issue.

I'll await for your feedback and corrections.