Added: Model for Web domain PHP directives

Quote from i-MSCP Github (hotfixes)

Code

1. Added: Model for Web domain PHP directives
2. Added: Model for user PHP editor permissions
3. Added: Model for user PHP editor limits
4. Small fixes

Source: https://github.com/i-MSCP/imsc…a78a31f8e2d8973b59ba5ddf8