#4607 No conflicts with nvim-lspconfig by default

Default `g:ale_disable_lsp` to a new mode `'auto'` by default. With this
setting applied, ALE will now check for the presence of nvim-lspconfig
and automatically turn off particular LSP linters if already configured
via nvim-lspconfig.

For users that do not use `nvim-lspconfig`, everything should work as
before.

ale_linters/swift/sourcekitlsp.vim

@@ -5,6 +5,7 @@ call ale#Set('sourcekit_lsp_executable', 'sourcekit-lsp')
 
 call ale#linter#Define('swift', {
 \   'name': 'sourcekitlsp',
+\   'aliases': ['sourcekit'],
 \   'lsp': 'stdio',
 \   'executable': {b -> ale#Var(b, 'sourcekit_lsp_executable')},
 \   'command': '%e',