Log reason why a Lua script fails to parse

Explains more why the script failed parsing. Also adds a `Game.AddChatLine` for why it fails.

![lua-error](https://cloud.githubusercontent.com/assets/566742/3822210/e4e9f4de-1d1e-11e4-847e-20eeb7d12daa.png)

I tested with

```
Fatal Lua Error: Error parsing shellmap.lua
Fatal Lua Error: Reason: [string "shellmap.lua"]:29: 'end' expected (to close 'function' at line 5) near '<eof>'
```

I think the second `Fatal Lua Error:` is redundant.