Widget type for entry in GUIs.

Cache entry values are always strings, but CMake GUIs present widgets to help users set values. The GUIs use this property as a hint to determine the widget type. Valid TYPE values are:

BOOL          = Boolean ON/OFF value.
PATH          = Path to a directory.
FILEPATH      = Path to a file.
STRING        = Generic string value.
INTERNAL      = Do not present in GUI at all.
STATIC        = Value managed by CMake, do not change.
UNINITIALIZED = Type not yet specified.

Generally the TYPE of a cache entry should be set by the command which creates it (set, option, find_library, etc.).