External Tools: Translate name and category

The external tools internally are stored in an ini-like file format:

    [Tool 0]
    category=Git
    name=git-cola
    ...

This patch adds grep/sed magic following how we extract translatable
strings from json files in KTextEditor (indenter, scripts).

Running the two grep lines create output like:

    // i18n: file: 8
    i18nc("External tool category", "Git");

This output is then extracted with the XGETTEXT call a line later.