Permit charts with same name.

[toonarmycaptain]

Creating a new chart with the same name will overwrite previous chart data in app data store.
This is not an issue for the user save function, as user can choose to overwrite existing file, or save the image with a different name.

Solution might be to try to save chart data file and if file already exists, append '_1' or' _(1)' to filename, iterating the integer until an existing file is not found. Might make more sense to start at '2' rather than one, although the convention at least on windows for duplicate filenames is to start at 1.

The image saving code should take the resultant filename, rather than repeating the process to save the image in the app data.

This would be elementary based on the chart id in SQL databases, if the json database is dropped. Otherwise maybe creating an id in chart data, and building up a list of charts at runtime, or maintaining a json list to load.

[toonarmycaptain]

GitMate.io thinks possibly related issues are #84 (Make chart images save in correct folder.), and #68 (Go straight from create class to new chart.).