Translation: Changed some translation keys.

We shouldn't use underscore + number suffix in normal translation keys, now that
they get added automatically by the translation system. So I changed
STR_WEAPON_1 to STR_WEAPON_ONE and STR_WEAPON_2 to STR_WEAPON_TWO.
Translation: More complete sentences.

- STR_EQUIPMENT_FOR_craftname
- STR_SELECT_SQUAD_FOR_craftname
Translation: Better support for number-forms.

- STR_n_UNITS_IN_EXIT_AREA
- STR_n_UNITS_OUTSIDE_EXIT_AREA
Translation: Proper question when abandoning game.

Only Spanish really needed this, but it's proper translation code.
- STR_ABANDON_GAME_QUESTION
Merge pull request #267 from karvanit/TranslatorFriendlyCode

Translator friendly code