Rename to atom from task

The variables, exception messages and
other variable namings in the atom file
should reflect atoms, not tasks (which
is a leftover change from when these
were in a different file).

Change-Id: Ie7870c8240409f7c53d4f2806eafa912bcc620b9
Warn about internal helper/utility usage

Adjust the utils doc and add in a warning that
lets users know that the internal functions and
modules that appear to be utility related should
not be used externally (and if they use these they
are using them at their own risk).

Change-Id: I5d813028c8c7f35359853cab45fcdc8454bbf6fd
Merge "Warn about internal helper/utility usage"