NUT-Monitor localization (engine?) needs fixes

[jimklimov]

There was some work done in #2845 and #2857 but still, when testing across OpenIndiana (py2 and py3), Ubuntu (py3) and Windows with MSYS2 (py2 and py3), there are discrepancies in how localization for the GUI is handled.

In some cases the footer (Error connecting to host, etc.) is not localized, in some cases the field labels, in some the menu names or their items, and rarely the About dialog. Sometimes the "Error connecting" on the first page did not appear at all (OI Py2 and Py3) although the Found N devices on hostname did appear with the serving hostname populated.

In Windows/MSYS2 there is also a problem loading/decoding (internal re-coding?) of the locale files, so they are not understood as UTF-8.

On OpenIndiana with "fr" locale, the main Py2 dialog window after login was very wide (over 1000px) for no apparent reason; Py3 was sized normally (but items were not localized).

One guess is that the _(string) localization methods/macros misfire somehow, probably with intermittent or end-of-block newlines (CR, CRLF, present or not at the end) which may be interpreted differently on various systems?..