Update common, decoder, encoder, java (#520)

Common:
 * wrap dictionary data into `BrotliDictionary` structure
 * replace public constant with getter `BrotliGetDictionary`
 * reformat dictionary data

Decoder:
 * adopt common changes
 * clarify acceptable instance usage patterns
 * hold reference to dictionary in state

Encoder:
 * adopt common changes
 * eliminate PIC spots in `CreateBackwardReferences`
 * add per-chunk ratio guards for q0 and q1
 * precompute relative distances to avoid repeated calculations
 * prostpone hasher allocation/initialization
 * refactor Hashers to be class-like structure
 * further improvements for 1MiB+ inputs
 * added new hasher type; made hashers more configurable

Java:
 * Pull byte->int magic to `IntReader` from `BitReader`