(#460) Extend license mapping for common SPDX license names (#509)

Fixes #460 
Signed-off-by: Christopher Angelo Phillips <christopher.phillips@anchore.com>

internal/spdxlicense/license_test.go

@@ -0,0 +1,60 @@
+package spdxlicense
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestIDParse(t *testing.T) {
+	var tests = []struct {
+		shortName string
+		spdx      string
+	}{
+		{
+			"GPL-1-only",
+			"GPL-1.0-only",
+		},
+		{
+			"GPL-2",
+			"GPL-2.0",
+		},
+		{
+			"GPL-2+",
+			"GPL-2.0+",
+		},
+		{
+			"GPL-3.0.0-or-later",
+			"GPL-3.0-or-later",
+		},
+		{
+			"GPL-3-with-autoconf-exception",
+			"GPL-3.0-with-autoconf-exception",
+		},
+		{
+			"CC-by-nc-3-de",
+			"CC-BY-NC-3.0-DE",
+		},
+		// the below few cases are NOT expected, however, seem unavoidable given the current approach
+		{
+			"w3c-20150513.0.0",
+			"W3C-20150513",
+		},
+		{
+			"spencer-86.0.0",
+			"Spencer-86",
+		},
+		{
+			"unicode-dfs-2015.0.0",
+			"Unicode-DFS-2015",
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.shortName, func(t *testing.T) {
+			got, exists := ID(test.shortName)
+			assert.True(t, exists)
+			assert.Equal(t, test.spdx, got)
+		})
+	}
+}