Implement array patterns

[yannham]

Depends on #1910.

This commit adds a new class of patterns: array patterns. This is a natural extension, both syntactically and semantically, of existing data structure patterns in Nickel (in particular of records). Similarly, arrays pattern can also capture the rest of the pattern (the tail of the array that hasn't been matched yet) and bind it to a variable.

[dpulls[bot]]

:tada: All dependencies have been resolved !