Better UI for HOT parameters

Currently parameters for HOT applications are asked in a random order because they are represented as a dictionary in HOT template and dictionaries are unordered by default. Parameter labels are generated from parameter key name using simple conversion to title format. However those visual aspects may be specified in HOT template. It can contain optional parameter_groups section that defines not only the order of properties but also groups them into several input steps. Parameters may contain optional label property that should be preferred over key name when present. Murano can make use of such HOT elements to improve user expirience