hamming: add hint to @Ignore annotations

SumOfMultiples : add hint to @Ignore annotations

binary-search-tree: replace lambda with method reference

luhn: add hints to @Ignore annotations

pythagorean-triplet : add hint to @Ignore annotations

etl: add hints to @Ignore annotations

grade-school: add hints to @Ignore annotations

wordy: add hints to @Ignore annotations

series: add hints to @Ignore annotations

robot-simulator: add hints to @Ignore annotations

minesweeper: add hints to @Ignore annotations

sublist: add hints to @Ignore annotations

CustomSetTest : add hint to @Ignore annotations

Clock : add hint to @Ignore annotations

ChangeCalculatorTest : add hint to @Ignore annotations

ListOpsTest : add hint to @Ignore annotations

simple-cipher: add hint to @Ignore annotations

palindrome-products: add hint to @Ignore annotations

#442

#443

#445

#445

#445

#446

#447

#473

#473

secret-handshake: add hint to @Ignore annotations

difference-of-squares: add hint to @Ignore annotation

space-age: add hint to @Ignore annotations

gigasecond: add hint to @Ignore annotations

pangram: add hint to @Ignore annotations

saddle-points: add hint to @Ignore annotations per #440

perfect-numbers: add hint to @Ignore annotations per #444

ref #448

Ref. #448