add function to detect advanced stepping commands
support advanced stepping commands when the are available
basic shortcut viewer (non-dismissable)
make keyboard shortcut overlay dismissable
assign shortcuts to groups
merge shortcuts for same command
preserve order of shortcuts in Commands.cmd.xml
override titles for shortcuts that don't have sensible menu names
more granular separation of shortcuts into categories
improve light-dismiss behavior for overlay
remove html shortcut help entry points
show only one key combination per shortcut
Merge remote-tracking branch 'origin/v0.98-shiny' into feature/shortcut-info

Conflicts:
	src/gwt/src/org/rstudio/studio/client/workbench/commands/Commands.cmd.xml
add some non-function-bound shortcuts (global and source editor)
Merge remote-tracking branch 'origin/master' into feature/shortcut-info
add some editor shortcuts
Fix bug: breakpoints don't work with NA constants such as NA_character_
Fix bug: Shiny breakpoints don't track editor line changes correctly
Fix bug: clicking on the line number itself shouldn't set a breakpoint
Fix bug: when debugging inside a fold, fold doesn't open automatically