Merge user-manual/ into user/ and drop some old/unused files

developer/libjamiclient-coding-style.md

developer/ui-ux-development.md

misc.rst

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uploads/6f3b937c07720d5b8c192ab3045cf4e0/.vsconfig

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uploads/97d9656f04fcdb2d714a6718d9f94241/vsconfig

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...403e2cd1573296709f4608/create_account_jami_android_EN.pdf

uploads/af663991871a742eb08ba623169c14d9/vsconfig.zip

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uploads/f01ac140971a9a0224cbd158eb858143/testJAMI.ods