Add remark for translators
Fix clashing shortcuts

Changed shortcuts for Blockquote to Ctrl+Shift+Q and for
Insert Image to Ctrl+Shift+I to prevent ambiguous shortcuts
on Linux.

Resolves #115.
Fix Word Wrap and Show Special Characters

Fixed the initial status of the word wrap and the
show special characters options.

- Use toggled() signal for the show special characters action
- Change default checked state for the word wrap action

Resolves #107