Saving changes in different location

[a-niem]

The original rod position files should not be overwritten anymore. Instead the user should place the files in a new directory.

• [x] a text field should be added to the UI where the saving folder is indicated
• [x] the saving folder path shall be changable by the user
• [x] suggested saving folders should have the form old_folder_path_corrected/
• [x] when the user changed the folder to old_folder_path a warning must be displayed before saving with the possibility to abort the saving process
• [x] the saving shall not be done directly after completing one rod placement/number change anymore. Instead a new Save button should be introduced.
• [x] There must appear a warning when the image is changed and unsaved changes are present

[a-niem]

This issue is resolved with #16