cache and components improvements

• 2Q cache:
  • added TTL
  • added cache update events
  • many unittests
• LRU cache:
  • uniform TTL management for 2Q and LRU caches
  • per item TTL
• HashMap
  • change grow_factor from 2 to 4 (as in std AA)
  • some code cleanup
• Lists
  • fix bug in SList postblit
• hash function
  • switch to core.internal.hash: bytesHash for string