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
Merge remote-tracking branch 'origin/master' into feature/shortcut-info

Conflicts:
	src/gwt/src/org/rstudio/studio/client/workbench/commands/Commands.cmd.xml
	src/gwt/src/org/rstudio/studio/client/workbench/commands/Commands.java
add some unbound editor shortcuts; combine unbound shortcuts by title
add concept of extended file types and simple test implementation for shiny
pickup all .r files in shiny extended type
provide a link to the 'full' shortcut docs from the quick reference card
rebalance columns, add some more unbound editor shorcuts