Autocomplete implementations of getter and setter methods

[keskiju]

User writes 'get' or 'set' while editing a class and autocomplete provides getter/setter implementation snippets for fields of a class. Also include "get/set all fields" suggestions and suggestions for constructor implementation. Maybe reuse some implementation logic from java-generator package?

Implement:

• [ ] AtomAutocompleteProvider.getSuggestions(): Implement constructor suggestions (empty constructor, constructor with class fields as parameters).
• [ ] AtomAutocompleteProvider.getSuggestions(): Implement getter/setter suggestions.
• [ ] AtomAutocompleteProvider.getSuggestions(): Implement suggestion that adds getter/setter for all fields that don't have one yet.

[keskiju]

3 and #4 should return suggestions only if cursor position is in 'class SomeClass { ... }' scope.