[BitBucketServer] Missing lines_of_code

Hello,

one thing I am missing is `lines_of_code` that was available in Ruby version of Danger. It helps to warn reviewers that PR is bigger than is standard or expected, or you can simply force documentation/tests update from certain number of lines like I did in Ruby danger:

```ruby
# Check if documentation is updated
documentation_warning = 10
documentation_error = 30
documentation_message = "Documentation was not updated. Any change should be reflected in DCS."
# Skip if is trivial
if has_app_changes && !has_documentation_changes
warn documentation_message if git.lines_of_code >= documentation_warning && (git.lines_of_code < documentation_error || is_trivial)
fail documentation_message if git.lines_of_code >= documentation_error && !is_trivial
end
```