Completion improvements

 * Guanako: Support return statements, various minor improvements
 * Valama: Determine current line in a more intelligent way (supports multiple statements in one line etc)
Valama: Made completion thread more reliable
Guanako: Initial support for embedded statements, escaped values
Guanako: Non-alphabetic prefixed proposals first
Initial refactoring support

 * Guanako: Support iterating through expressions
 * Valama: Allow jumping to a symbol's declaration
 * Valama: Improved current file structure behaviour
Initial reference finding support

 * Guanako: Support finding references of an object
 * Valama: Made search widget more flexible, show reference finding results
Initial line-by-line execution support

 * Guanako: Frankenstein: Line-by-line breakpoints. Still a little stupid, but works unless there are multiple statements per line.
 * Valama: GUI for line-by-line execution