Refactor frequently used functions into a utils folder

The following functions/files are in the materials folder, but are also used by geometry and user_defined properties:

• material/property_classes/socket_properties.py
• TemplatePanel class in material/ui.py
• draw_sockets_list function in material/ui.py

User defined properties panel i.e. define_prop folder has functions used in ui.py, operators.py and properties.py such as:

• in operators.py and collection_UD_props.py an import is needed from .ui import attr_get_type, get_attr_only_str, get_obj_str
• operators.py has a attr_set_val function which could be integrated into attr_get_type
• one prop needs to

Randomise all and save parameters panel i.e. random_all folder:

• Repeated codes from operators.py for each of the panels: camera transforms, materials, geometry and UD props

Renaming of UD props functions and variables and add note in docs:

• # should be renamed candidate UD props
  list_sckt_names_in_graph in collection_UD_socket_properties.py
• sockets naming in UD props, not actually sockets but socket-like
• empty UIlist causes issues for other functionality (see #90 )

Start by tracing the listed functions in material/property_classes/socket_properties.py, material/ui.py, define_prop/operators.py, collection_UD_props.py, and collection_UD_socket_properties.py, then compare repeated code in random_all/operators.py. Done means shared functions are organized in a utils folder, callers are updated, UD-prop naming and documentation are clarified, and the empty UIList issue from #90 is addressed.