Started work on adding mod downloader

Read from mod-list.json in mod dir and download each mod in list.
This requires reading from factorio mod portal api, and extracting download url and calling it with username and api token.

new field in config.yml username and apitoken, is needed to download mod files from mod.factorio.com

jsonStruts.go

@@ -0,0 +1,37 @@
+package main
+
+type Mod struct {
+	Name    string `json:"name"`
+	Enabled bool   `json:"enabled"`
+	Version string `json:"version,omitempty"`
+}
+
+type ModList struct {
+	Mods []Mod `json:"mods"`
+}
+
+type ModPortal struct {
+	Category      string    `json:"category"`
+	DownloadCount int       `json:"downloads_count"`
+	Name          string    `json:"name"`
+	Owner         string    `json:"owner"`
+	Releases      []Release `json:"releases"`
+	Score         float64   `json:"score"`
+	Summary       string    `json:"summary"`
+	Thumbnail     string    `json:"thumbnail"`
+	Title         string    `json:"title"`
+}
+
+type Release struct {
+	DownloadUrl string   `json:"download_url"`
+	Filename    string   `json:"file_name"`
+	InfoJson    InfoJSON `json:"info_json"`
+	ReleaseTime string   `json:"released_at"`
+	Sha1        string   `json:"sha1"`
+	Version     string   `json:"version"`
+}
+
+type InfoJSON struct {
+	Dependencies    []string `json:"dependencies"`
+	FactorioVersion string   `json:"factorio_version"`
+}