Allow use of project list in Jira module config

For my own use case (and anyone in a similar situation), the Jira
module is more useful if I can specify a list of projects to
display issues from, rather than no project (which selects all
projects) or one specific project.

New supported syntax:
`  project: ["PROJA", "PROJB"]`

If this is merged, documentation for the Jira module should be
updated accordingly. (Sorry, I would have done this myself but
I'm not sure what the right place is - when grepping I find
multiple places in the repo containing documentation strings
and I'm not sure what the "master" location is)

Specifying a single project (or no project) is still supported -
behavior shouldn't change for anyone who doesn't change their
config.

jira/widget.go

@@ -25,7 +25,7 @@ func NewWidget() *Widget {
 /* -------------------- Exported Functions -------------------- */
 
 func (widget *Widget) Refresh() {
-	searchResult, err := IssuesFor(Config.UString("wtf.mods.jira.username"), Config.UString("wtf.mods.jira.project", ""), Config.UString("wtf.mods.jira.jql", ""))
+	searchResult, err := IssuesFor(Config.UString("wtf.mods.jira.username"), getProjects(), Config.UString("wtf.mods.jira.jql", ""))
 
 	widget.UpdateRefreshedAt()
 
@@ -81,3 +81,21 @@ func (widget *Widget) issueTypeColor(issue *Issue) string {
 
 	return color
 }
+
+func getProjects() []string {
+	// see if project is set to a single string
+	configPath := "wtf.mods.jira.project"
+	singleProject, err := Config.String(configPath)
+	if err == nil {
+		return []string{singleProject}
+	}
+	// else, assume list
+	projList := Config.UList(configPath)
+	var ret []string
+	for _, proj := range projList {
+		if str, ok := proj.(string); ok {
+			ret = append(ret, str)
+		}
+	}
+	return ret
+}