SandwichDB move ctor issue

[ony]

Wrong move ctor for SandwichD:

auto foo = SandwichDB();
// foo.meta.sandwich points to foo
foo->Open(/*...*/);
auto boo = std::move(foo);
// boo.meta.sandwich points to *old* foo

Because meta copied as is instead of being re-created in new place it will refer to freed memory used for old SandwichDB.

[ony]

Unit-test for both gcc 4.7 and 4.8:

TEST(Simple, sandwich_move_issue14)
{
    auto db = std::move(leveldb::SandwichDB<leveldb::MemoryDB> {});
    (void) db.use("alpha");
}