Create first automated UI test

List of aspects to test in the first UI test:

• plugin build + installation
• create new Quarkus project
• add extensions
• build it using maven, test if build is successful
• check for exceptions

Here is a github issue to add first automated UI test:

• https://github.com/redhat-developer/intellij-quarkus/issues/216

List of aspects to test in the following UI tests (github issues will be created for them):

• Completion support for Quarkus properties
• Hover support for Quarkus properties
• Validation support for Quarkus properties
• Support for Quarkus profiles
• Outline support (flat or tree view)
• Wizards
• Code assist
  ...