Add central policies document

simple-linked-list: add hint to @Ignore annotations

bracket-push: add hint to @Ignore annotations

binary-search-tree: use Collections.singletonList

Fixes: #512

Fixes: #513

book-store: add hint to @Ignore annotation

ocr-numbers: add hint to @Ignore annotations

strain: add hint to @Ignore annotations

rectangles: add hint to @Ignore annotations

meetup: add hint to @Ignore annotations

triangle: add hint to @Ignore annotations

robot-name: add hint to @Ignore annotations

largest-series-product: add hint to @Ignore annotations

matrix: add hint to @Ignore annotations

nth prime: add hint to @Ignore annotations

isogram: add hint to @Ignore annotations

nucleotide-count: add hint to @Ignore annotations

phone-number: add hint to @Ignore annotations

diamond: add hint to @Ignore annotations

word-count: add hint to @Ignore annotations

flatten-array: add hint to @Ignore annotations

pascals-triangle: add hint to @Ignore annotations

sieve: add hint to @Ignore annotations

twelve-days: add hint to @Ignore annotations

queen-attack: add hint to @Ignore annotations

linked list: add hint to @Ignore annotations

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