Move all static content from jsps to servlets

[zzz]

jsps with nothing but Java code for serving static content was started by jrandom and has been proliferated in the years since.

This is inefficient as we must handle last-modified and other headers and responses ourselves, and we don't handle things like range headers. Jsp + things like FileUtil? replace efficient Jetty nio handling. We also have to set outbound headers like content-type.

By using a Servlet and setting the resource, most of that will be handled for us. To be replaced:

flags.jsp
viewhistory.jsp
viewtheme.jsp
viewrouterlog.jsp
viewwrapperlog.jsp

[zzz]

make new package net.i2p.router.web.servlets
move CodedIconRendererServlet? from helpers to servlets
add new servlets there
see also #2270

[zzz]

Moved CodedIconRendererServlet? in d01f663ed5061112379b1df0b1cc642494fe9355 to be 0.9.35-1