Configurable CasaOS installation path

[leaf918]

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Describe the bug 安装在x86主机上，nas根没有大空间，casa默认安装到根目录下导致失败

To Reproduce Steps to reproduce the behavior: bash casaos.sh

Expected behavior A clear and concise description of what you expected to happen.

Screenshots If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS: x86 liunx
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Additional context Add any other context about the problem here. 期望可以定义安装位置。

[Lauren-ED209]

This is a necessary feature. It happens that we are opitmizing the bash script recently. Let's evaluate this feature in recent development version! I will manage to update our evaluation result here. ;)

[ETWang1991]

The new installation script, allows for smaller space installations, but we still recommend that you install with more than 4GB of space. And for some reason, some components must be installed in the default location.

[tigerinus]

@leaf918 你的截图显示根分区剩余空间是 0GB

所以确认一下：你的 NAS 即使剩余空间 0GB 也能正常跑么？