Fix problems with lexicon edit popup

[jtmaxwell3]

This fixes some minor problems with the lexicon edit popup:

• Removes the lexicon edit popup from the list of lexicon tools in the Lexicon panel.
• Consolidates the logic for choosing the dictionary configuration for the lexicon edit popup into GetInnermostConfigurationDirectory.

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This change is 

[mark-sil]

@mark-sil reviewed 3 files and all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @jtmaxwell3).