image->data change

[decarlof]

I realized that the pull request changing image->data may create some confusion because there are some variable derived from data called image (see imageTag, imageTag_label etc.).

Also there are some locations, for example in the old 2IDE HDF files in file_loader.py, still showing

self.dataTag.addItem('images')

I propose to change all variable derived from data as dataXXX

[sichendart]

self.dataTag.addItem('images') is for legacy. In the new hdf, "image" changes to "data", but not in the old files.

[decarlof]

ok that makes sense. I was also concerned about

    `img_tag = self.imageTag.currentText()`
    `data_tag = self.dataTag.currentText()`
    `self.parent.params.image_tag = self.imageTag.currentText()`
   ` self.parent.params.data_tag = self.dataTag.currentText()`

in the same