[Java/Feigh] Don't HTML escape Accept / Content-Type header

When e.g. the Accept-Header contains special characters such as `=`, mustache escapes them, which results in code like this to be generated:

```java
// MyApi.java
public interface MyApi extends ApiClient.Api {
  @RequestLine("GET /rest/protected/items?size={size}&page={page}")
  @headers({
      "Content-Type: */*",
      "Accept: application/com.example+json; version=1.0; charset=utf-8,application/com.example+xml; version=1.0; charset=utf-8,application/json; charset=utf-8,application/xml; charset=utf-8",
  })
  LicenseListResource getLicenses(@QueryMap(encoded=true) Map<String, Object> queryParams);
}
```

Note the `Accept: application/com.example+json; version&#x3D;1.0; charset&#x3D;utf-8` with the escaped `=`, which does not work. This disables HTML escaping for the header values.

On a side note though, I had been wondering whether HTML escaping makes sense when generating Java files? It does in JavaDocs I suppose, but shouldn't it be disabled everywhere else?

Author: blutorange

src/main/resources/handlebars/Java/libraries/feign/api.mustache

@@ -40,10 +40,10 @@ public interface {{classname}} extends ApiClient.Api {
   @RequestLine("{{httpMethod}} {{{path}}}{{#hasQueryParams}}?{{/hasQueryParams}}{{#queryParams}}{{baseName}}={{braces "left"}}{{paramName}}{{braces "right"}}{{#has this 'more'}}&{{/has}}{{/queryParams}}")
   @Headers({
   {{#vendorExtensions.x-contentType}}
-      "Content-Type: {{vendorExtensions.x-contentType}}",
+      "Content-Type: {{{vendorExtensions.x-contentType}}}",
   {{/vendorExtensions.x-contentType}}
   {{#vendorExtensions.x-accepts}}
-      "Accept: {{vendorExtensions.x-accepts}}",
+      "Accept: {{{vendorExtensions.x-accepts}}}",
   {{/vendorExtensions.x-accepts}}
   {{^vendorExtensions.x-accepts}}
       "Accept: */*",
@@ -85,13 +85,13 @@ public interface {{classname}} extends ApiClient.Api {
   @RequestLine("{{httpMethod}} {{{path}}}?{{#queryParams}}{{baseName}}={{braces "left"}}{{paramName}}{{braces "right"}}{{#has this 'more'}}&{{/has}}{{/queryParams}}")
   @Headers({
   {{#vendorExtensions.x-contentType}}
-      "Content-Type: {{vendorExtensions.x-contentType}}",
+      "Content-Type: {{{vendorExtensions.x-contentType}}}",
   {{/vendorExtensions.x-contentType}}
   {{^vendorExtensions.x-contentType}}
       "Content-Type: */*",
   {{/vendorExtensions.x-contentType}}
   {{#vendorExtensions.x-accepts}}
-      "Accept: {{vendorExtensions.x-accepts}}",
+      "Accept: {{{vendorExtensions.x-accepts}}}",
   {{/vendorExtensions.x-accepts}}
   {{#headerParams}}
       "{{baseName}}: {{braces "left"}}{{paramName}}{{braces "right"}}"{{#has this 'more'}},{{/has}}