Proposal to implement collapsing #500

1. Add new setting "go.blockImportsOnly" 2. Add parsing of package name for single import lines 3. When the user adds an import manually and there is already one or more single imports, collapse it all into a block if go.blockImportsOnly is true.

1. Fix linter issues

1. Back out package name parsing 2. Remove setting from package.json (always use block imports) 3. Switch up how block import is created to preserve comments and special imports