Use proper strings

[juanfra]

Here it goes again.

Modified the strings, according to #164 and https://make.wordpress.org/core/handbook/best-practices/spelling/#abbrev iations-and-acronyms

I'm not sure if I should update the translation catalogs or if you do that before each release.

[vedanshujain]

Hi @juanfra , thanks so much for sending this. If you have time, would you please rebase this with latest master so that we merge this ? Apologies for the stagnation. Also, I think we would need to propagate these changes to language files as well, so that we do not break the translations.