Do not purge apache configs by default

If the user of this module did not define the apache class
it would be included with all apache defaults in init.pp.  Since
the apache default is to purge configs this would remove any custom
apache configuration on a server.
Added manage_apache parameter to allow user to completely bypass the apache module inclusion
Updating tests to support not managing apache by default

Since the module is no longer managing apache by default, the module
is assuming that users have instantiated their own apache class
somewhere else in their manifest.  So the test cases will assume the
same and incldue 'apache' as a pre_condition
Allow a user to be an admin of more than one trac instance

This adds some hacky code that gets around puppet's current lack
of iteration support.  It is especially trickey since the iteration
is being done insiade a defined type, which means the same iteration
loop could be required multiple times.  So if it looks strange, even
to those familiar with the define loop pattern, that's why.  I tried
to explain it in the code comments.