Improve displayed strings

Problem/Motivation

Please always use "A/B test" instead of "test" in strings, to make sure translations can be done correctly.

Steps to reproduce

Proposed resolution

Rename the strings like:
Test name > A/B test name
Add test > Add A/B test
Edit test > Edit A/B test
The test has been created. > The A/B test has been created.
The test has been updated. > The A/B test has been updated.
Test ID: > A/B test ID:
How does this tool work? > How does this A/B test tool work?
etc

Remaining tasks

User interface changes

API changes

Data model changes