Fix MS-DOS line endings

Somehow sfdb_freesound_mootcher.cc has ended up with MS-DOS style line
endings again. Put it back to UNIX-style.
Remove Soundcloud upload from export format specification

Remove the Soundcloud upload property from export formats - it doesn't
belong there, since it's a thing which can apply (or not) to any format
preset.
Make Soundcloud upload applicable to any export format.

Add soundcloud_upload property back into ExportFormatSpecification, but
instead of making it settable in the export format specification dialog,
add a tick-box in each tab of ExportFileNotebook to allow setting it.
Better names for Soundcloud-related members of ExportHandler

Rename the Soundcloud-related members of ExportHandler to all begin with
soundcloud_, and rename a couple of members of SoundcloudExportSelector
too for consistency.
Visual tweaks to Soundcloud panel

Re-arrange the items in the Soundcloud panel into a more sensible order &
arrangement, and add a (not-yet functional) tick-box to set the uploaded
files to be downloadable.
Show URI of file uploaded to Soundcloud in log window.
Set 'downloadable' property on Soundcloud uploads

Set the downloadable property according to what the user chose on files
uploaded to Soundcloud.
Remove Soundcloud export format presets

Now that Soundcloud export isn't a persistent property of export presets,
these are of no use whatsoever.
Add and use a DEBUG flag for Soundcloud uploads.

Replace output to stdout/stderr from Soundcloud upload functions with
DEBUG_TRACE (DEBUG::Soundcloud, ...).