Enable/disable plugins using the config file instead of folder name

**Is your feature request related to a problem? Please describe.**
I have been working on some plugins development and others are too. Currently the way to activate plugins is to rename the folders and remove the `disabled-` prefix

**Describe the solution you'd like**
Using the `zeronet.conf` file to enable/disable plugins.

**Describe alternatives you've considered**
I haven't considered other solution.

**Additional context**
No.

Start by tracing how plugin activation currently depends on folder names and how zeronet.conf is read. Define the configuration format and its precedence over the disabled- prefix, then verify that plugins can be enabled and disabled through zeronet.conf without renaming folders.

由索引模型根据 Issue 内容生成。