New functions and configurable keyboard shortcuts

* Added "General" and "Shortcuts" settings tab.
* Made all keyboard shortcuts configurable (with modifier)
* Added option "Restore tabs"
* Added option "Single instance"
* Added function "Delete line(s)" 
* Added menu entry and keyboard shortcut option for: 
  * "Save All" 
  * "Find Next" 
  * "Find Previous" 
* Function "Go to line" reacts on Return key
* Changed handling of config read error: They will be shown in the Error List
* Set focus on start to text input 
* Added opt-in feature "Save all on compile" 
* Changed main window title to "file - Aporia" (saved) or "file* -Aporia" (unsaved)
* Re-order the columns in the Error List
* Show Errors in the Error List in red
* Activate Error List when an error ocurs (optional)
* Scroll to last error when an error ocurs
* Add config entry activateErrorTabOnErrors 
* Activate "Output" tab on program run after compilation