Correct minor spelling issues

Problem/Motivation

There were some minor issues with several sentences, as explained in #2841432-7: [D7] Only One.

Proposed resolution

Attached patch provides some corrections and alternatives to several front-end sentences (inline comments and phpdoc blocks have not been fully checked).
Good luck with the application!

Remaining tasks

None.

User interface changes

None.

API changes

None.

Data model changes

None.