Previously, the properties that applied to the BuildInfo task itself
and those that would be written into the build-info.properties file
were all configured on BuildInfo directly. This lack of separation
could be confusing.

This commit rework BuildInfo to separate the task's own properties
from those that are written into the build-info.properties file.

The task has also been updated so that changes to a project's
properties made after the task has been configured are reflected in
the build info properties.