Add Scope For Alias and Package Name of Import Declarations

[joefitzgerald]

This adds two new scopes:

• entity.alias.import.go
• entity.name.import.go

This allows import declarations to be tokenized, and prevents them from being recognized as quoted strings. This paves the way for package autocompletion for single and multi-line import declarations:

Single line import

import "fmt"

Single line import with alias

import aliasedfmt "fmt"

Multi line import

import (
    "fmt"
)

Multi-line import with alias

import (
    aliasedfmt "fmt"
)

Fixes joefitzgerald/go-plus#226
Requires joefitzgerald/autocomplete-go#50 to allow autocompletion in import statements

[winstliu]

I think the strings should still get the customary string.quoted.double.go/punctuation.definition.string.begin/end.go scopes.

[joefitzgerald]

A string is a go type. The text inside the package portion of an import declaration is not a string.

[joefitzgerald]

I take that back: https://golang.org/ref/spec#ImportPath. The spec does define an import path as a string literal. Will add that back in.

[winstliu]

Maybe use \\s* instead of \\s??