[Stellarium-pubdevel] [Draft] Add l10n support for plugins

[Alexander W. <ale...@gm...>]

Short instructions.

For add l10n support for plugins need in each plugins include
StelLocaleMgr.hpp and marked all UI text strings as translatable
(q_("") or N_("")).

Example for AngleMeasure:

In includes block:
#include "StelLocaleMgr.hpp"

In plugins info (description) block:
StelPluginInfo AngleMeasureStelPluginInterface::getPluginInfo() const
{
        // Allow to load the resources when used as a static plugin
        Q_INIT_RESOURCE(AngleMeasure);

        StelPluginInfo info;
        info.id = "AngleMeasure";
        info.displayedName = q_("Angle Measure");
        info.authors = q_("Matthew Gates");
        info.contact = "http://porpoisehead.net/";
        info.description = q_("Provides an angle measurement tool");
        return info;
}

In sources list using q_("") or N_("") for translatable text. And add
file names with includes translatable lines in POTFILES.in into
po/stellarium folder

Notes:
1. Need refactoring painter.drawText lines - example in AngleMeasure plugin
2. Need refactoring HTML text in UI-files - example in Oculars (tab
"About" in GUI)

-- 
With best regards, Alexander