Wal e recovery

Add LWRP for wal-e envdir.
Add seperate recovery and archive recipes for wal-e.

@mbautin 
@vnivargi 
In other words, it could just be
```ruby
      variables config: {
        restore_command: "envdir #{env_dir} wal-e wal-fetch \"%f\" \"%p\""
      }.merge(node['postgresql']['recovery']['config'])
```