Add Intellisense in proxy.config

[nicogis]

Add Intellisense VS in proxy.config

[bsvensson]

Thanks @nicogis for helping improve the resource-proxy!

[bsvensson]

FYI: it looks like after this commit, users of the DotNet proxy, need to update their proxy.config as in the commit 3f00000#diff-619e6e6c6786d5cebe866bfb1ab4492f

If you update your resource-proxy for DotNet, but keep your old proxy.config as is, your proxy will probably break saying [InvalidOperationException: <ProxyConfig xmlns=''> was not expected.]

Basically, the DotNet proxy is now "stricter", and you just have to change from
<ProxyConfig allowedReferers="*" mustMatch="false">
in your proxy.config to
<ProxyConfig allowedReferers="*" mustMatch="false" xmlns="proxy.xsd">