Multiple configuration files

[symphorien]

Fixes #431

With

let g:LanguageClient_settingsPath = [ '~/.config/lsp_global_settings.json', '.vim/settings.json' ]

you get a global configuration which can be enriched and overridden by a local one.
The merging is done in the standard way (apparently RFC 7396) via the json-patch crate.

[autozimu]

Thanks!