Update to FCS 0.0.73 and Fantomas 1.6.0

Lots of breaking changes in FCS.
Fix unit tests
Pretty print return types of events

Close #676 (now supported from upstream).
Handle a part of #683.
Pretty print attributes correctly based on current context

Fix #699.
Merge pull request #800 from dungpa/fcs

Improve Go to metadata feature using FCS 0.0.73