Remove replace_ argument for files_filtered again

[MSeifert04]

The replace_ argument was basically a good idea but as #559 and #557 show whitespaces are not the only problematic character. - is quite frequently used and sometimes even .. Other invalid characters for keyword arguments are quite rare.

However it might be better to just document the workaround (passing in an unpacked dictionary) than actually inventing a functionality that tries to cover these cases in an easy to use way.

If we make replace_ a dictionary for characters to translate that will be very awkward to use (because you could end up inventing different placeholders for different characters) and when you're passing in a dictionary already one might as well pass in the dictionary containing the key-value pairs.

Note that replace_ hasn't been released yet so this doesn't need a deprecation.

[MSeifert04]

xref: #481 #539

[mwcraig]

Any thoughts on this, @bsipocz?

[mwcraig]

Ideally we'd talk about this in the narrative documentation, but I think those need a much larger overhaul that makes sense as part of ccdproc 2.0, so I'm merging this as-is.