Robotframework-mobilelibrary

> * optimize gif feature
> * add new KW: Mobile Swipe In Element

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> * optimize gif feature
use diff flag for mobilelib(mobile_gif=true) & weblib(web_gif=true) and fix some bugs(issues/18)

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> * fix hot bugs(issues/3)
a bug invoked by the new feature -gif

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> * add New KWs
Mobile_Press_Keycode Mobile_Long_Press_Keycode
> * add New function
Support to generate one gif file for each test case with the flag(gen_gif_flag).
Library AppiumLibrary gen_gif_flag=True
Note: Now only support in solo, can't used in mix with web
> * fix some bugs(issues/5)
fix the bug 'Mobile Click WebView TextElement' can't work on android 6.x

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> * add New KWs
Mobile_Wait_Until_Text_Exist Mobile_Wait_Until_Element_Exist Mobile_Wait_Until_Text_Vanish Mobile_Wait_Until_Element_Vanish
Mobile_Get_Text_Button_Num
> * optimize the timeout/log/description of KWs
> * fix some bugs(issues/22)

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