Pick cacheOnTimeout and render limit from mapnik config

- adds default mapnik configuration values
 - removes old top-level mapnik config, rely on renderer one

lib/cartodb/server_options.js

@@ -33,9 +33,16 @@ module.exports = function(redisPool) {
 
     var rendererConfig = _.defaults(global.environment.renderer || {}, {
         cache_ttl: 60000, // milliseconds
-        metatile: 4,
+        statsInterval: 60000,
+        mapnik: {
+            poolSize: 8,
+            metatile: 2,
             bufferSize: 64,
-        statsInterval: 60000
+            snapToGrid: false,
+            clipByBox2d: false,
+            limits: {}
+        },
+        http: {}
     });
 
     var me = {
@@ -63,11 +70,6 @@ module.exports = function(redisPool) {
           mapnik_tile_format: global.environment.mapnik_tile_format || 'png',
           default_layergroup_ttl: global.environment.mapConfigTTL || 7200
         },
-        mapnik: {
-          poolSize: rendererConfig.poolSize,
-          metatile: rendererConfig.metatile,
-          bufferSize: rendererConfig.bufferSize
-        },
         statsd: global.environment.statsd,
         renderCache: {
             ttl: rendererConfig.cache_ttl,
@@ -269,8 +271,8 @@ module.exports = function(redisPool) {
             function handleTilerLimits(err, renderLimit) {
                 assert.ifError(err);
                 rendererOptions.limits = {
-                    cacheOnTimeout: global.environment.enabledFeatures.cacheOnTimeout || false,
-                    render: renderLimit
+                    cacheOnTimeout: rendererConfig.mapnik.limits.cacheOnTimeout || false,
+                    render: renderLimit || rendererConfig.mapnik.limits.render || 0
                 };
                 return null;
             },