ENH: Assert bundle tractograms and data in bundling script

[jhlegarreta]

Assert bundle tractograms and data in bundling script according to the set of expected bundles:

• Make sure that all config files involved contain all the bundles existing in the anatomy file.
• Filter any other tractogram file in the atlas folder.

Add the necessary helper methods and definitions.

Add the corresponding tests.

Fixes #57.

[jhlegarreta]

inform the user about the presence of other files in the atlas folder that do not correspond to the bundle names in the anatomy config files

I chose not to inform the user about it; I think it is enough with filtering the files that are not relevant; by providing a config, it is understood that the user is aware of the target bundles.

[jhlegarreta]

Package testing failures are unrelated; PR #59 was opened to try to address them, but it looks like the dependency solver is unable to find a solution for pandas. Needs to be investigated, but the current PR is good as it is.

[stale]

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