Fix removing standard custom encoders and decoders

[DarkVoyage]

According to changelog this was fixed in 2.2.3. I've tried removing them again and they reappear again.
I've already configured needed external encoders and decoders and want to remove these "examples".

[c72578]

„Removing of manually added Encoders or Decoders“ has been fixed. See: #201

[c72578]

@DarkVoyage Thanks for your report.
The current behavior is unusual concerning deleting of predefined external Encoders or Decoders.
Two possibilities:

• Either gray out (disable) delete for predefined external Encoders or Decoders.
• Or allow deleting of predefined external Encoders or Decoders and do not let them reappear.

[ha-korth]

• Or allow deleting of predefined external Encoders or Decoders and do not let them reappear.

They would reappear if the settings.txt file were ever deleted and a new default settings.txt file created.
To expand on the 'gray out' proposal. How about a setting to 'enable' external 'CommandLine' Encoders or Decoders?
Users have to supply the .exe to get these to work anyway so why not have them disabled by default and grayed-out in the GUI and advanced settings unless each external Encoder or Decoder is enabled?

{
= "$type": "CUETools.Codecs.CommandLine.EncoderSettings, CUETools.Codecs",
= "Name": "flac.exe",
= "Extension": "flac",
= "Enable": false, <<<<<<<<<<
= "Lossless": true,
= "SupportedModes": "0 1 2 3 4 5 6 7 8",
= "EncoderMode": "5",
= "Path": "flac.exe",
= "Parameters": "-%M -P %P - -o %O"
= },

[DarkVoyage]

I don't think it is a big problem to allow removing them completely. If user wants to restore them he can delete settings ini.