Integrate blockarray_t into pagecache_impl_t

1. Rename relasecached_pagecacheimpl into emptycache_pagecache
2. Add convenience macros to pagecache_t which allows to call
   the all interface functions of pagecache_it.
3. Add parameter "pagecache_t pgcache" to blockarray_t.
   This allows blockarray_t to use a pagecache_t during initialization
   phase where the global pagecache_t service is available.
4. Add blockarray_t to pagecache_t and replace linear search in list
   with array access.
5. Extend module memory/vm.h with functions
   initaligned_vmpage(/*out*/vmpage_t * vmpage, size_t powerof2_size_in_byte
   and log2pagesize_vm().
6. log2pagesize_vm value is cached in valuecache_t
7. Change order of initialization.
   pagecache_impl_t now comes first and then mmtransient_t.