Add support for internationalization

.gitignore

Makefile

bitmask.pro

build.sh

gui/i18n/base.ts

gui/i18n/main_ar.ts

gui/i18n/main_es.ts

gui/i18n/main_es_ES.ts

gui/i18n/main_nl.ts

gui/i18n/main_pl.ts

gui/i18n/main_pt_BR.ts

gui/main.cpp

gui/qml/AboutDialog.qml

gui/qml/DonateDialog.qml

gui/qml/LoginConfirmation.qml

gui/qml/LoginDialog.qml

gui/qml/main.qml

tools/transifex/Makefile

tools/transifex/main.go

tools/transifex/messages.json