feat(benchpress): show more metrics and make the run mode configurable

Shows the metrics:
script, render, gcAmount, gcAmountInScript, gcTime

Run modes:
- detect: auto detect whether to force gc
- forceGc: forces a gc before every run and ignores no runs
- noGcInScript: ignore runs that have gc while a script was executing
- plain: does not force gc nor ignore runs

Closes #368

modules/benchmarks_external/e2e_test/compiler_perf.es6

@@ -29,14 +29,9 @@ function runClickBenchmark(config) {
   var buttons = config.buttons.map(function(selector) {
     return $(selector);
   });
-  var timeParams = browser.params.benchmark;
-  benchpress.runBenchmark({
-    sampleSize: timeParams.sampleSize,
-    targetCoefficientOfVariation: timeParams.targetCoefficientOfVariation,
-    timeout: timeParams.timeout,
-    metrics: timeParams.metrics,
-    logId: browser.params.lang+'.'+config.logId
-  }, function() {
+  var params = Object.create(browser.params.benchmark);
+  params.logId = browser.params.lang+'.'+config.logId;
+  benchpress.runBenchmark(params, function() {
     buttons.forEach(function(button) {
       button.click();
     });