[FEATURE] remove yarn, update to latest node, speed up installation process

.yarnrc

-# THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY.
-# yarn lockfile v1
-
-
-lastUpdateCheck 1495625859628
-yarn-offline-mirror "sgc-packages-offline-cache"
-yarn-offline-mirror-pruning true

core/node.sh

-nodeversion="8.2.1"
+nodeversion="10.9.0"

install.sh

@@ -57,9 +57,10 @@ echo -e "\033[0;32mNode installed ✓\033[0m\n"
 # install node deps
 echo -e "\033[0;34mInstall dependencies\033[0m";
 rm -rf ./node_modules
-npm install yarn@0.27.5
 
-node_modules/yarn/bin/yarn install
+npm set progress=false
+npm ci --prefer-offline
+npm set progress=true
 echo -e "\033[0;32mDependencies installed ✓\033[0m\n"
 
 # copy config file if no present yet