This is a huge change, which includes some changes to replace code that
originally cloned to reuse allocations instead. The updated
`elastic-array` crate renames its consuming `Vec`-conversion method to
`into_vec`, which means that I can do a simple
`sed -i 's/to_vec/into_vec/'` and then fix the compilation errors.
This commit is probably a minor performance win and definitely a
significant readability win.
* Create new column family for local node info
* remove DBTransaction::new reliance on DB
* KeyValueDB trait
* InMemory KeyValueDB implementation
* journaldb generic over KVDB
* make most of `ethcore` generic over KVDB
* fix json tests compilation
* get all tests compiling
* implement local store (just for transactions)
* finish local store API, test
* put everything into place
* better test for skipping bad transactions
* fix warning
* update local store every 15 minutes
* remove superfluous `{}`s
