support f=lry, f=nmf, f=kmz that will give back file attachment

[esoekianto]

Based on this documentation, list of supported format in REST API includes f=lyr, f=nmf, f=kmz and so on, http://resources.arcgis.com/en/help/arcgis-rest-api/index.html#/Output_formats/02r3000000wq000000/

When we do this, "http://services.arcgisonline.com/arcgis/rest/services/world_physical_map/mapserver?f=lyr", we actually get the actual lyr file as download file, but when we proxy it "http://localhost/proxy.ashx?http://services.arcgisonline.com/arcgis/rest/services/world_physical_map/mapserver?f=lyr", then we get "proxy.ashx" as download file

[MehulChoksey]

Content of the file is as expected(its a layer file and not the proxy source.). Only The name of the file gets changed to proxy.*
Same is the case with jsp and php as well.

[esoekianto]

@afili @jgravois we need to watch out for header "Content-Disposition: attachment; filename='xxxxx'"

[esoekianto]

proposed fix for JSP #113

[esoekianto]

#114 would better handle this

[afili]

proposed fix #134 will handle this