Allows display_size to use a fixed unit for easy comparison of
multiple results, and fixed decimal places for the same reason.

Improves behaviour by using consistent decimal places and a
consistent space before the unit (the previous one only has a space
before 'bytes', not before 'KB').

Of existing uses, all the ones that displayed a 'maxbytes' type
configuration setting (which are likely to have an 'exact' size
and would be better shown as 512 KB rather than 512.0 KB) have been
changed to use 0 decimal places, to preserve previous behaviour.
All the uses which were showing an actual file or memory size have
been left as default (1 decimal place).

This report filter can be used for filtering reports by given
duration, via selection of time value and unit (seconds, minutes,
hours, etc).

The patch allows for strings welcomeback and welcometosite to be
customised and use other user names than just the firstname.

Supported are placeholder properties matching all known name fields:
firstnamephonetic, lastnamephonetic, middlename, alternatename,
firstname and lastname. Special values fullname and alternativefullname
are supported, too.

By default, the firstname is kept for compatibility with the original
feature design.

* Plus use example domain for user email in the Behat test