introduce option for JSON output

Also rename printHomeserverMemberCount option accordingly to fit new
output type.

roominfotree/roominfotree.go

@@ -20,29 +20,29 @@ type homeserverServerVersionInfo struct {
 type RoomInfoTree map[id.RoomID](*RoomInfo)
 
 type RoomInfo struct {
-	MemberCount     uint
-	GivenAliases    []string
-	Aliases         []string
-	MaxRoomVersions map[string](*MaxRoomVersionInfo)
+	MemberCount     uint                             `json:"memberCount"`
+	GivenAliases    []string                         `json:"givenAliases"`
+	Aliases         []string                         `json:"aliases"`
+	MaxRoomVersions map[string](*MaxRoomVersionInfo) `json:"maxRoomVersions"`
 }
 
 type MaxRoomVersionInfo struct {
-	MemberCount uint
-	Servers     map[string](*ServerInfo)
+	MemberCount uint                     `json:"memberCount"`
+	Servers     map[string](*ServerInfo) `json:"servers"`
 }
 
 type ServerInfo struct {
-	MemberCount uint
-	Versions    map[string](*VersionInfo)
+	MemberCount uint                      `json:"memberCount"`
+	Versions    map[string](*VersionInfo) `json:"versions"`
 }
 
 type VersionInfo struct {
-	MemberCount uint
-	Homeservers map[string](*HomeserverInfo)
+	MemberCount uint                         `json:"memberCount"`
+	Homeservers map[string](*HomeserverInfo) `json:"homeservers,omitempty"`
 }
 
 type HomeserverInfo struct {
-	MemberCount uint
+	MemberCount uint `json:"memberCount"`
 }
 
 var unknownServerVersionInfo = fclient.Version{