Merge pull request vnpy#3171 from vnpy/dev

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Merge pull request vnpy#3145 from vnpy/dev

2.6.0正式合并

Merge pull request vnpy#3109 from vnpy/dev

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Merge pull request vnpy#3028 from vnpy/dev

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Merge pull request vnpy#2976 from vnpy/dev

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Merge pull request vnpy#2915 from vnpy/dev

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Merge pull request vnpy#2843 from vnpy/dev

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Merge pull request vnpy#2777 from vnpy/dev

[Mod] import from QtWidgets instead of QtGui

Merge pull request vnpy#2710 from vnpy/dev

[Mod] update version number

Merge pull request vnpy#2672 from vnpy/dev

Dev