Schema analysis improvements

[aalexandrov]

TODOs (@jkovacs)

• Forward-analysis from the Function parameters -> (Ff, Ef) (via LNF.Meta.valuses).
• Backward-analysis from the return expr -> (Fb, Eb) (via LNF.Meta.valdefs).
• Final results of local schema analysis is (Ff ∪ Fb, closure(Ef ∪ Eb)) (or perhaps (Ff ∩ Fb, closure(Ef ∩ Eb))).
• Support for nested case classes / tuples (e.g. (Int, (String, String), Double).
• Design a small example for potential projection projection, e. g. carrying both the first and the last names across if-else conditions where only the last name is used.

TODOs (@aalexandrov)

• Proper return type for LNF.Meta.valuses.
• Specify the possible simple expression patterns.