#13 Adds support to gets the TV tuner's channel list (via HTTP)

[Rosfran Borges]

In order to removes all the dependency to the MySQL from the main GMyth example applications, we need to allows to use the HTTP interface to get all the channels available in the MythTV backend server.
Suggestion: to add a function call named gmyth_http_get_channel_list, to the gmyth/gmyth_http.h