Implement code peek feature in the IDE - phase 1

We should implement the code peek feature. For example, by pressing a hotkey, the declaration of the symbol under the cursor is shown in a source code viewer popup. By using this, users do not need to jump to other locations in the source code to quickly check the declaration.

Tasks:

• create a custom ttcn3 source viewer control
• add a new command (hotkey, context menu) -> added to F9 key