修复PageView bugs，NText支持设置字体，NImage、VImage和背景支持本地资源

[jimmysuncpt]

1. 当PageView设置自动滑动时，用户拖动时禁止自动滑动；
2. 解决PageView内存泄漏问题；
3. NText支持设置assets目录下的字体文件；
4. NImage支持设置本地资源（drawable、mipmap）；
5. VImage支持设置本地资源（drawable、mipmap）；
6. 所有控件背景图片支持设置本地资源（drawable、mipmap）。

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