1.针对浏览器的Preflight请求做统一处理，避免出现报错不支持post请求；
2.修正文件路径拼接方式；
3.修正部分接口的参数解析和封装；

修复DokitUtil.param2Json bug

[documentation] - fix grammar in contributing.md

iOS内部图片使用xcasset；deployment_target = '9.0'

1, 修正在转义字符串到Json时有key无value异常

1、更新文档，添加官方调查问卷

MOD: DoraemonManager 增加一个支持的旋转方向属性, 可在任意位置调用, 实时生效.

1、add android dokit v3.2.0 & 3.1.8.0

# Conflicts:
#	Android/java/app/build.gradle
#	Android/java/app/doraemonkit.gradle
#	Android/java/build.gradle
#	Android/java/buildSrc/src/main/kotlin/com/didichuxing/doraemonkit/plugin/DoKitTransformInvocation.kt
#	Android/java/buildSrc/src/main/kotlin/com/didichuxing/doraemonkit/plugin/transform/DoKitBaseTransform.kt
#	Android/java/config.gradle
#	Android/java/doraemonkit-no-op/upload.gradle
#	Android/java/doraemonkit-plugin/src/main/kotlin/com/didichuxing/doraemonkit/plugin/DoKitTransformInvocation.kt
#	Android/java/doraemonkit-plugin/src/main/kotlin/com/didichuxing/doraemonkit/plugin/transform/DoKitBaseTransform.kt
#	Android/java/doraemonkit-plugin/upload-dev.gradle
#	Android/java/doraemonkit-rpc/upload-dev.gradle
#	Android/java/doraemonkit-weex/upload-dev.gradle
#	Android/java/doraemonkit-weex/upload.gradle
#	Android/java/doraemonkit/src/main/java/com/didichuxing/doraemonkit/kit/filemanager/bean/DirInfo.kt
#	Android/java/doraemonkit/src/main/java/com/didichuxing/doraemonkit/kit/uiperformance/UIPerformanceManager.java
#	Android/java/doraemonkit/upload-dev.gradle
#	Android/java/settings.gradle