Add install locally feature

[luc-yang]

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As github.com is not always accessable in China, could you please add addinstall locally feature for CasaOS?

[jifeiyun]

腾讯轻云服务器 安装两天 终于安装上了..... 太慢了

[ETWang1991]

This issue will be addressed in the following new requirements https://github.com/IceWhaleTech/CasaOS-Doc/issues/124

[haust-lyb]

The installation script does not work in the Medieval continent , so sad o(╥﹏╥)o

[tigerinus]

temporary workaround:

1. download all .tar.gz from each CasaOS-* release page (see list)

    CASA_PACKAGES=(
        "${CASA_DOWNLOAD_DOMAIN}IceWhaleTech/CasaOS-Gateway/releases/download/v0.4.0/linux-${TARGET_ARCH}-casaos-gateway-v0.4.0.tar.gz"
        "${CASA_DOWNLOAD_DOMAIN}IceWhaleTech/CasaOS-MessageBus/releases/download/v0.4.0/linux-${TARGET_ARCH}-casaos-message-bus-v0.4.0.tar.gz"
        "${CASA_DOWNLOAD_DOMAIN}IceWhaleTech/CasaOS-UserService/releases/download/v0.4.0/linux-${TARGET_ARCH}-casaos-user-service-v0.4.0.tar.gz"
        "${CASA_DOWNLOAD_DOMAIN}IceWhaleTech/CasaOS-LocalStorage/releases/download/v0.4.0/linux-${TARGET_ARCH}-casaos-local-storage-v0.4.0.tar.gz"
        "${CASA_DOWNLOAD_DOMAIN}IceWhaleTech/CasaOS-AppManagement/releases/download/v0.4.0/linux-${TARGET_ARCH}-casaos-app-management-v0.4.0.tar.gz"
        "${CASA_DOWNLOAD_DOMAIN}IceWhaleTech/CasaOS/releases/download/v0.4.0/linux-${TARGET_ARCH}-casaos-v0.4.0.tar.gz" 
        "${CASA_DOWNLOAD_DOMAIN}IceWhaleTech/CasaOS-CLI/releases/download/v0.4.0/linux-${TARGET_ARCH}-casaos-cli-v0.4.0.tar.gz" 
        "${CASA_DOWNLOAD_DOMAIN}IceWhaleTech/CasaOS-UI/releases/download/v0.4.0/linux-all-casaos-v0.4.0.tar.gz" 
    )

2. Decompress all files under the same directory

There should be a build folder as result

3. Run wget get.casaos.io/install.sh to get the install script locally.

4. Run sudo bash install.sh -p ./build

@luc-yang