Allow passing multiple files to Script.Reference
Lazily load config insead of using cctor

Loading config can fail due to external errors. This is not an
appropriate thing to do in a static constructor. The 'real error' can be
hidden at runtime in a TypeInitializationException. See
http://ericlippert.com/2013/02/18/static-constructors-part-four/
and
http://csharpindepth.com/Articles/General/Singleton.aspx
Don't load assemblies which don't reference HotGlue.Core

Don't load assemblies which don't reference HotGlue.Core, because they
probably don't contain types we need, and loading them can cause errors
we don't care about if they're buggy.
Add options arg for Script.Reference; no header/footer

You can now pass an optional options argument for
HotGlue.Script.Reference.
Right now the only option is GenerateHeaderAndFooter, which can be set
false to suppress generation of <script> etc tags when you want to
control this yourself instead of having Hotglue do it for you.