Allow defaults in lambda arguments
Emit lambda parameter defaults if existant
Remove necessity to use the object operator for chaining except when ambiguous
Rewrite grammar slightly, solving 31 shift/reduce conflicts
Remove funny-looking invoke-operator `$a.()` / `$this.func.()`
Replace by `$a()` (obviously), `($this.func)()` to disambiguate
Merge pull request #38 from xp-lang/feature/lambda-defaults

Feature: lambda defaults