This method retrieves all the subscriptions applying some filters:
* Filtering out by [[SubscriptionPurchaseType]] = Top-down)
* Filtering out by GetDeviceTypeFilter the type of device the user is logged on (Depending if is OTT, IPTV or Hybrid)
* Filters them depending on the typeFilter parameter provided (see [[SubscriptionType]]). If no typeFilter is provided, this method returns all the subscriptions.