connected v0.7.3

Connected changes for v0.7.3:

• changed design of resizer gizmo
• changed Condition, Switch and SetVar nodes so they're resizable now (width only)
• added a link to the online docs for creating/changing node types (pro only) in the top menu
• added an About window in the top menu

So yes, v0.7.3 finally adds the necessary documentation for those who want to create their own node types! If there's anything missing, please don't hesitate to tell me.