[ticket/12730] Add Google+ profile field

I had to create a new custom profile field type since Google+ formats URLs differently for integer IDs and custom URLs. For custom URLs it adds a + before the URL which makes it hard to validate or format, created a new offshoot of type_string in order to compensate for that.
```
FILE: ...is/build/phpbb/phpbb/phpBB/phpbb/profilefields/type/type_googleplus.php
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FOUND 1 ERROR(S) AFFECTING 1 LINE(S)
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51 | ERROR | Inline control structures are not allowed
| | (Generic.ControlStructures.InlineControlStructure.NotAllowed)
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```

Please add { and }