Handle multi-line ExtensionManifest element
Handle multi-line ExtensionManifest element

Use xml.dom.minidom to parse the ExtensionManifest element
when extracting the panel ID and name from the manifest.xml file.
By doing it this way we no longer require that the attributes are
in a single line.

Fixes #27

adobe-photoshop/generator-panels,adobe-photoshop/generator-panels,adobe-photoshop/generator-panels