Use a single memoryLimit instead of memory and memorySwap

We will make the percent allocation dynamic depending on the system.

When we have servers with a large amount of RAM but little swap, we
seem to use a lot of swap because of 50% allocation strategy. In such
systems, we run out of swap and thus have OOM errors even though there
is a lot of RAM available!

src/settings.js

@@ -451,11 +451,6 @@ function getPlatformConfig(callback) {
 function setPlatformConfig(platformConfig, callback) {
     assert.strictEqual(typeof callback, 'function');
 
-    for (let addon of [ 'mysql', 'postgresql', 'mail', 'mongodb' ]) {
-        if (!platformConfig[addon]) continue;
-        if (platformConfig[addon].memorySwap < platformConfig[addon].memory) return callback(new BoxError(BoxError.BAD_FIELD, 'memorySwap must be larger than memory', { field: 'memory', addon }));
-    }
-
     settingsdb.set(exports.PLATFORM_CONFIG_KEY, JSON.stringify(platformConfig), function (error) {
         if (error) return callback(error);