AN-8888: Normalize the uri before loading data in EpubServer

[ZakHsieh]

If a URI contains HTML URL encoding will cause EpubServer fails to load that resource. This patch will normalize URL(s) before loading to resolve URI cannot be loaded in EpubServer.

[danielweck]

I reviewed the code "on paper" (i.e. I did not try it myself with edge cases such as HTML escape entities in URL syntax), and it all makes sense, PR looks safe to merge.

However I hope others will review / test the code too :)