Add ExtendedSolver

[sugyan]

resolve #4

benchmark:

running 6 tests
test bench_extended_default_hashmap ... bench: 305,348,742 ns/iter (+/- 11,777,141)
test bench_extended_zobrist_hashmap ... bench: 300,957,800 ns/iter (+/- 12,625,870)
test bench_extended_zobrist_vec     ... bench: 304,344,761 ns/iter (+/- 28,833,659)
test bench_normal_default_hashmap   ... bench: 470,923,483 ns/iter (+/- 98,406,580)
test bench_normal_zobrist_hashmap   ... bench: 462,357,119 ns/iter (+/- 42,716,992)
test bench_normal_zobrist_vec       ... bench: 473,962,235 ns/iter (+/- 70,757,369)

test result: ok. 0 passed; 0 failed; 0 ignored; 6 measured; 0 filtered out; finished in 703.30s