Combine CharsetConverterDialog, MainClearBriefcasePreferencesWindow, and MainFormUploaderWindow

[yanokwa]

The main class in Briefcase is org.opendatakit.briefcase.ui.MainBriefcaseWindow, but there is code for three smaller utilities with the following main classes:

org.opendatakit.briefcase.ui.CharsetConverterDialog converts CSVs to UTF-8
org.opendatakit.briefcase.ui.MainClearBriefcasePreferencesWindow clears Briefcase preferences
org.opendatakit.briefcase.ui.MainFormUploaderWindow uploads blank forms to Aggregate instances

This functionality should be combined into a single binary.

A good first step would be to propose a single, combined user interface (where is the different functionality accessed from?).

[yanokwa]

I wanted to summarize some of the discussions @lognaturel, @ggalmazor, and I had.

For MainFormUploaderWindow, @ggalmazor has filed #462 to solve this.

For MainClearBriefcasePreferencesWindow, we should remove that code. Clearing preferences is mostly a developer task and so making that available on the command line seems good enough.

For CharsetConverterDialog, I propose we remove that code. According to https://opendatakit.org/downloads/download-info/odk-csvconverter-v1-4-3-production-jar/, it converts CSVs from a non-UTF-8 character encoding to UTF-8, presumably for Collect. It's been downloaded ~4000 times which isn't that large of a number. Seems more reasonable to

1. Ask that people use Unicode CSVs
2. If Collect sees a non-Unicode CSV, fail or do the conversion

[ggalmazor]

Closing since all the alternative UIs have been taken care of and there's an option to pull individual forms from disk.