Merge pull request #123 from DO-CV/fix-image-processing-module

[MAINT] Fix image processing module.
Remove FileSystem source files.
Remove FileSystem source files.
Merge branch 'maint-remove-filesystem-source-files' of https://github.com/DO-CV/DO-CV into maint-remove-filesystem-source-files
Merge pull request #125 from DO-CV/maint-remove-filesystem-source-files

[MAINT] Remove `FileSystem` source files.
Merge branch 'develop' into maint-test-linear-filtering