Set up URL escaping for Freemarker

[OndraZizka]

Freemarker can escape URLs, but it needs the default encoding to be set.

${post.uri?url}

To do URL encoding, the framework that encloses FreeMarker must specify the "output_encoding" setting or the "url_escaping_charset" setting, so ask the programmers to set them. Or, as a last chance, you can set the url_encoding_charset setting in the template, e.g. <#setting url_escaping_charset='ISO-8859-1'>, or give the charset explicitly to the built-in, e.g. foo?url('ISO-8859-1').

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FTL stack trace ("~" means nesting-related):
	- Failed at: ${post.uri?url}  [in template "index.ftl" at line 10, column 34]

[jonbullock]

PR for this #614