Changes to how you add shaders in the UI (#182)

* fix(shader): Prevent resetting parameters in shader settings

Introduce an early return check for the shader's variation. If the selected variation is the same as the previously active one, the function exits early, preventing any unnecessary resetting of shader parameters.

Fix #180

* feat(material): New way of adding shaders

- The shaders will now be automatically loaded in a EnumProperty through the data path set in addon preferences
- This includes a operator that will migrate the old "source" property over to the new "shader" enum property (and preserve all the other shader related data)
- Made it possible to add "material_name" to the load_shader and load_shader_variation operators so it can be called through API without needing to have a active object with a active material to run the operators

* Added support to export new shader setup

addon/i3dio/node_classes/material.py

@@ -175,11 +175,16 @@ def _write_properties(self):
             self._write_attribute('alphaBlending', True)
 
     def _export_shader_settings(self):
+        data_path = bpy.context.preferences.addons['i3dio'].preferences.fs_data_path
         shader_settings = self.blender_material.i3d_attributes
-        if shader_settings.source != shader_picker.shader_unselected_default_text:
-            shader_file_id = self.i3d.add_file_shader(shader_settings.source)
+        if shader_settings.shader != shader_picker.shader_default:
+            shader_path = data_path + "shaders\\" + shader_settings.shader + ".xml"
+            if shader_settings.shader == shader_picker.shader_custom and shader_settings.custom_shader != '':
+                shader_path = shader_settings.custom_shader
+            shader_file_id = self.i3d.add_file_shader(shader_path)
             self._write_attribute('customShaderId', shader_file_id)
-            if shader_settings.source.endswith("mirrorShader.xml"):
+
+            if shader_settings.shader == "mirrorShader":
                 params = {'type': 'planar', 'refractiveIndex': '10', 'bumpScale': '0.1'}
                 xml_i3d.SubElement(self.element, 'Reflectionmap', params)