[jsfm] Merge jsfm 0.21 features into 0.16-dev

[Hanks10100]

Details

• [rax] Upgrade weex-rax-framework to 0.4.7 .
• [rax] Add reliable type check for the last argument of taskCenter.send.
• [vue] Upgrade weex-vue-framework to 2.4.2-weex.3 . (change log)
• [vue] Support the <richtext> component.
• [vue] Fix the $refs in vue.
• [runtime] Support to return values in fireEvent.
• [vanilla] Remove the global id variable and the first parameter of sendTasks.
• [legacy] Support to use the computed class list in legacy framework.
• [legacy] Add warnings for legacy api on Array.prototype and Object.prototype.
• [legacy] Return instance in createInstance.

[weex-bot]

	Fails
🚫	Code file html5/frameworks/legacy/core/array.js does not have the copyright header.
🚫	Code file html5/frameworks/legacy/core/object.js does not have the copyright header.
🚫	Code file html5/runtime/normalize.js does not have the copyright header.
🚫	Code file packages/weex-js-framework/index.min.js does not have the copyright header.
🚫	Code file packages/weex-js-runtime/index.min.js does not have the copyright header.
🚫	Code file packages/weex-legacy-framework/index.min.js does not have the copyright header.

	Warnings
⚠️	No Changelog changes!
⚠️	These new JS files do not have Flow enabled: html5/runtime/normalize.js, packages/weex-js-framework/index.js, packages/weex-js-framework/index.min.js, packages/weex-js-runtime/index.js, packages/weex-js-runtime/index.min.js, packages/weex-legacy-framework/index.js, packages/weex-legacy-framework/index.min.js
⚠️	This PR modify SDK code without add/modify testcases.
⚠️	This PR should update related documents as well.

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