Blender Git Loki

Support tagging operator properties as 'advanced'

This will later be used to show advanced operator properties separate from
basic (as in non-advanced) ones in the UI.

Tagging a single operator property in C should be done via
`WM_operatortype_prop_tag()`. It does additional checks for type safety
that `RNA_def_property_tags()` doesn't do.

To avoid having to tag each advanced property individually, multiple
ones can be tagged by wrapping them into
`WM_operatortype_props_advanced_bein()` and
`WM_operatortype_props_advanced_end()` calls. It's also possible to only
call `_begin()`, all properties added after this will get tagged then.
In most cases this last approach should be sufficient.

Example of Python usage:
`my_float = bpy.props.FloatProperty(name="Some Float", tags={'ADVANCED'})`