Add an option for disabling plugins using local config ~/.vimrc.plugins

[timss]

Most settings, if not all, are possible to override using the local configuration files $HOME/.vimrc.{first,last}. Additional plugins can be added using $HOME/.vimrc.plugins.

One major caveat or limitation of the current setup is that plugins included in the main configuration can't be disabled or fully ignored using the local configuration. It should be possible to define a list of plugins that should never be installed, or otherwise allow users to disable plugins in the local configuration.

For instance:

let g:plugs_disabled = ['syntastic'] # or
UnPlug 'scrooloose/syntastic'

There are some similar solutions out there for vim-plug and other plugin managers today, usually solved in the vim distribution and not the plugin manager itself:

• Idea: variable to disable registration of plugin junegunn/vim-plug#442
• Option to Disable a Plugin junegunn/vim-plug#469
• https://github.com/spf13/spf13-vim#removing-disabling-an-included-plugin
• https://github.com/spf13/spf13-vim/blob/3.0/.vimrc.bundles#L62

[timss]

Not sure why GitHub removed the referenced commit.

1b4f629