Clear the status after typing in manual mode
Added a subclass hook for determining if a linter can lint a language
Moved highlight related constants to highlight.py
can_lint_language subclass hook is only called the first time executable path is determined
Added ctrl+shift+e as a key equivalent for show_all_errors command
Only show errors on save in save modes
Select command fixes/enhancements...

- Fixed a bug when the selection was empty.
- If the caret is at the beginning/end of an error, next/previous error will select that error instead of the next/previous error.
- Selecting an error from the Show All Errors panel now selects the entire error.