Source:

```md
- Evan You

<template slot="projects">

    - Vue.js
    - VueX

</template>
```

Usage:

```
<Content/> // get default slot
<Content slot="projects"> // get named slot
```

This reverts commit 04723be4.

1. Refine ExtendPageDataOption, simplify the implmentation
2. Introduce LayoutDistributor as the unique route layout entry
3. Inject layout components to LayoutDistributor
4. Register layout components located at themedir/layouts
5. Reorganize the default theme's structure

1. Support scope package and shortcut like plugin.
2. Support relative path for 'layout' and 'notFound' option.