Filters that read files should use capitalization agnostic comparisons

[imikejackson]

When a filter is looking for a specific file extension those comparisons are made against a constant string which is lower case. If the file's extension has a different capitalization then the filter will throw an error.

Most likely we need to throw in a .toLower() for the file extension QString.

[imikejackson]

BlueQuartzSoftware/SIMPL#349