Array support by Config.

Here is a simple array implementation. It's possible now to map something like this
```
connection.mysql.drive = mysql
connection.mysql.spec = user:pass@localhost:3306
connection.pgsql.drive = pgsql
connection.pgsql.spec = postgres:pass@dbhost:5432
```
into
```
map[
    mysql:map[
        driver : mysql 
        spec  : user:pass@localhost:3306
    ] 
    pgsql:map[
        driver : postgres 
        spec  : postgres:pass@dbhost:5432
    ]
]
```