CFG: Implemented the GetConfigInfoBlk2 function.

Added a "config" file to the CFG process service (CFG:U), and added a few default blocks to it.

Implemented GetSystemModel and GetModelNintendo2DS
Change this (imo quite confusing) loop to:
```c++
for (int i = config->total_entries - 1; i >= 0; --i) {
    // Ignore the blocks that don't have a separate data offset
    if (config->block_entries[i].size > 4) {
        offset = config->block_entries[i].offset_or_data +
            config->block_entries[i].size;
        break;
    }
}
```
(And then getting rid of the now redundant `total_entries` local variable, which was badly named to begin with.)