Some optics and keybindings changed, Localization added

- The optical changes are optional but in my personal opinion it looks better now. 
- There should not be a menu divider at the end of the menu. I removed it but it would be better to check if there are any following entries. 
- Shortcuts to collapse/expand all code regions are too much in my opinion because the usage of these commands is probably less than the problems caused by key conflicts.
- "cursor: pointer" does not work for individual elements since CodeMirror suppresses pointer-events of .CodeMirror-lines elements, so I removed it.
- Localization added.