bugfix GLFW delete/backspace/return keys were not coming in. also ctrl-click alt-click were not coming in as left right click. closes #2197

Note that for the key presses I translate:

```
GLFW_KEY_RIGHT_SHIFT to OF_KEY_SHIFT  
GLFW_KEY_RIGHT_ALT to OF_KEY_ALT
GLFW_KEY_LEFT_CONTROL to OF_KEY_CTRL 
```

so we get an event for OF_KEY_SHIFT / OF_KEY_ALT / OF_KEY_CTRL

I'm curious what you think about this @arturoc 

we could also fire two events? 
ie: 

ofNotifyKeyPressed(OF_KEY_RIGHT_ALT);
ofNotifyKeyPressed(OF_KEY_ALT);