A loader for loading a .pdb resource.
		The Protein Data Bank file format is a textual file describing the three-dimensional structures of molecules.
		
		// instantiate a loader
		var loader = new THREE.PDBLoader();
		// load a PDB resource
		loader.load(
			// resource URL
			'models/molecules/caffeine.pdb',
			// called when the resource is loaded
			function ( pdb ) {
				var geometryAtoms = pdb.geometryAtoms;
				var geometryBonds = pdb.geometryBonds;
				var json = pdb.json;
				console.log( 'This molecule has ' + json.atoms.length + ' atoms' );
			},
			// called when loading is in progresses
			function ( xhr ) {
				console.log( ( xhr.loaded / xhr.total * 100 ) + '% loaded' );
			},
			// called when loading has errors
			function ( error ) {
				console.log( 'An error happened' );
			}
		);
		
		[example:webgl_loader_pdb]
		[page:LoadingManager manager] — The [page:LoadingManager loadingManager] for the loader to use. Default is [page:LoadingManager THREE.DefaultLoadingManager].
Creates a new [name].
See the base [page:Loader] class for common properties.
See the base [page:Loader] class for common methods.
		[page:String url] — A string containing the path/URL of the .pdb file.
		[page:Function onLoad] — (optional) A function to be called after loading is successfully completed. The function receives the object having the following properties. [page:BufferGeometry geometryAtoms], [page:BufferGeometry geometryBonds] and the [page:Object JSON] structure.
		[page:Function onProgress] — (optional) A function to be called while the loading is in progress. The argument will be the XMLHttpRequest instance, which contains [page:Integer total] and [page:Integer loaded] bytes.
		[page:Function onError] — (optional) A function to be called if an error occurs during loading. The function receives the error as an argument.
		
Begin loading from url and call onLoad with the parsed response content.
[page:String text] — The textual pdb structure to parse.
		Parse a pdb text and return a JSON structure.
		
[link:https://github.com/mrdoob/three.js/blob/master/examples/js/loaders/PDBLoader.js examples/js/loaders/PDBLoader.js]