Merge similar translation strings in WordPress 4.7

[ramiy]

Some strings can be merged to reduce the total amount of strings.

[pedromendonca]

This is a great work being done here!
Congratulations @ramiy :)

[SergeyBiryukov]

@ramiy, thank you for the patches! Here's my review:

• 38808-welcome.patch​: The non-breaking space is required to prevent wrapping on About page.
• 38808-sticky.patch​: Looks good, we're not checking a particular post here.
• 38808-assign-terms.patch​: The existing strings are more accurate, there's a difference between assigning terms in general, assigning a particular term, and assigning several terms in a single request.
• 38808-invalid.patch​: Mostly looks good, I've found a few more instances that could be adjusted for consistency.
• 38808-search-results.patch​: That string is used for title and should be capitalized.
• 38808-delete-resource.patch​: Looks good.
• 38808-no-results.patch​: Looks good.
• 38808-updating.patch​: The existing string seems correct.
• 38808-allow-comments.patch​: Strings in wp_xmlrpc_server::initialise_blog_option_info() don't have a full stop, while strings in register_initial_settings() do have one. They could probably be merged or updated, but let's create a separate ticket for that.
• 38808-delete-post.patch​: Looks good, we're checking a particular post here.

38808.combined.patch​ is my take on the changes.

[SergeyBiryukov]

In 39278:

Text Changes: Merge some duplicate strings with the same meaning in error messages, adjust some other strings for consistency and accuracy.

Props ramiy, SergeyBiryukov.
Fixes #38808.