[activemq] add Ubuntu support

These files are provided by default with an Ubuntu ActiveMq installation.

Fixes: GH#271

Signed-off-by: Adam Stokes <adam.stokes@ubuntu.com>
[archive] log add_string exception

Log any permission related exceptions when running plugins as non-root.
Eventually this information can be reviewed to see the impact of running
plugins as non-root users to better decide where root is needed on a per
plugin basis.

References #164

Signed-off-by: Adam Stokes <adam.stokes@ubuntu.com>
[Makefile] makefile tasks to work with python2 and 3

Fixed some of the inline python statements to support makefile rules
in both python2 and python3

Signed-off-by: Adam Stokes <adam.stokes@ubuntu.com>
[docs] add policies api reference

Include the base policy plugin reference in the auto-generated
documentation.

Signed-off-by: Adam Stokes <adam.stokes@ubuntu.com>