Updating client dependencies. Switching to yarn. (#6433)

* Updating client dependancies. Switching to using yarn.

* Updating React

* Moving pure components to using function syntax (performance gains with newer react version)

* Updating client dependancies.

* Ignore .yarninstall

* Enabling pre-lockfile because it's the entire point of using yarn.

* Removing old webpack config

* Moving to new prop-types

* Fixing ESLint Errors

* Updating jest snapshots.

* Cleaning up package.json

webapp/Makefile

@@ -2,37 +2,37 @@
 
 BUILD_SERVER_DIR = ..
 
-check-style: .npminstall
+check-style: .yarninstall
 	@echo Checking for style guide compliance
 
-	npm run check
+	yarn run check
 
-test: .npminstall
+test: .yarninstall
 	cd $(BUILD_SERVER_DIR) && $(MAKE) internal-test-web-client
 
-.npminstall: package.json
-	@echo Getting dependencies using npm
+.yarninstall: package.json
+	@echo Getting dependencies using yarn
 
-	npm install
+	yarn install --pure-lockfile
 
 	touch $@
 
-build: .npminstall
+build: .yarninstall
 	@echo Building mattermost Webapp
 
 	rm -rf dist
 
-	npm run build
+	yarn run build
 
-run: .npminstall
+run: .yarninstall
 	@echo Running mattermost Webapp for development
 
-	npm run run &
+	yarn run run &
 
-run-fullmap: .npminstall
+run-fullmap: .yarninstall
 	@echo FULL SOURCE MAP Running mattermost Webapp for development FULL SOURCE MAP
 
-	npm run run-fullmap &
+	yarn run run-fullmap &
 
 stop:
 	@echo Stopping changes watching
@@ -51,4 +51,4 @@ clean:
 
 	rm -rf dist
 	rm -rf node_modules
-	rm -f .npminstall
+	rm -f .yarninstall