Missing features todo list

[hendricha]

• [x] Don't open empty tab if nothing is returned by syfi-cli
• [x] Throw a normal message if AppKernel or bootstrap.php.cache could not be found
• [x] app folder location should be configurable
• [x] locate twig shorthands
• [x] locate doctrine model shorthands
• [ ] if nothing is selected get the first relevant string around the caret
• [ ] parse 'use' for class names from the current file
• [ ] locate where a service id is defined
• [ ] handle translation source to target conversion somehow and open where translation is used