[5.0] Accomodate Multiple Autoloaded Folders

At the moment `getAppNamespace()` breaks if you have multiple source folders set in composers PSR-4 setting as it expects a string but is an array. This just first checks if its an array first then handles accordingly.
ie
This works fine
```
"psr-4": {
	"Ntech\\": "app/"
}
```
But this breaks
```
"psr-4": {
	"Ntech\\": [ "app/" , "src/" ]
}
```