New form widget for binary(BLOB) fields added issue #3151

[selmaVH1]

fixes #3151 and fixes #3148
@DelazJ @timlinux
I added this as a Tip in https://docs.qgis.org/testing/en/docs/user_manual/managing_data_source/create_layers.html#creating-a-new-geopackage-layer subsection. I tried to describe whole workflow but didn't find logical place in documentation for that.

[DelazJ]

Thanks @selmaVH1
Considering that this type of field is not specific to gpkg only, it is probably a bit hidden imho. We also already mention few lines above that it can store blob fields, so could be enough.
How about https://docs.qgis.org/testing/en/docs/user_manual/working_with_vector/vector_properties.html#edit-widgets? I think right now it is the place widgets options and behavior are described, and this one (which is the default for blob field type) is missing there.
Another feature I came across recently is the combination of this kind of field type with an html widget, to eg display an image directly in form. See for reference https://gis.stackexchange.com/questions/350541/display-photo-stored-as-blob-in-gpkg; I think this deserves a mention in the docs (in the html widget section or the blob's one, no strong opinion). What do you think?

[selmaVH1]

@DelazJ I added Binary(BLOB) to edit widgets section and another feature (HTML and BLOB combination) I described as a Tip simply because of the size of description.

[elpaso]

Suggested change

	whether the BLOB field is empty or not. If filed is not empty the content size
	whether the BLOB field is empty or not. If the field is not empty the content size

?