Add more validation on the UI field: groupId

[IvoNet]

Add validation to the groupId field in the starter UI

GroupId should only allow:

• lowercase names
• names starting with [a-z]
• dot as separators
• no hyphens ('-') but underscores ('_')
• no spaces
• etc.
  see also here: guide-naming-conventions

[geziefer]

I could do this together with #274

[geziefer]

artifactId must start with a letter and then contain any number of letters, digits or underscore - the following regex was used: "^[a-zA-Z][a-zA-Z0-9_-]*$"/>

This was addressed in PR #292

[m-reza-rahman]

Fixed.