Add missing data types

[vaind]

model/properties.py currently handles the most common types. The missing types supported by ObjectBox should be added, e.g. date.

The list of currently supported objectbox types (as of objectbox-c v0.10.0):

typedef enum {
 OBXPropertyType_Bool = 1, ///< 1 byte
 OBXPropertyType_Byte = 2, ///< 1 byte
 OBXPropertyType_Short = 3, ///< 2 bytes
 OBXPropertyType_Char = 4, ///< 1 byte
 OBXPropertyType_Int = 5, ///< 4 bytes
 OBXPropertyType_Long = 6, ///< 8 bytes
 OBXPropertyType_Float = 7, ///< 4 bytes
 OBXPropertyType_Double = 8, ///< 8 bytes
 OBXPropertyType_String = 9,
 OBXPropertyType_Date = 10, ///< Unix timestamp (milliseconds since 1970) in 8 bytes
 OBXPropertyType_Relation = 11,
 OBXPropertyType_DateNano = 12, ///< Unix timestamp (nanoseconds since 1970) in 8 bytes
 OBXPropertyType_ByteVector = 23,
 OBXPropertyType_StringVector = 30,
} OBXPropertyType;

[greenrobot]

Scalar types were added via #11