Make commands.properties optional for non-ACS code

Currently any new API extension to CloudStack must edit
commands.properties to add the appropriate ACLs.  This generally works
fine for ACS as we control the contents of that file and distribute
all the code ourself.  The hang up comes when somebody develops code
outside of ACS and want to add their code to an existing ACS
installation.  The Spring work that has been done has made this much
easier, but you are still required to manually edit
commands.properties.  This change introduces the following logic.

First check commands.properties for ACL info.  If ACL info exists, use
that to authorize the command.  If no ACL information exists (ie
null), then look at the @APICommand annotation.  The defaults of
@APICommand will provide no ACL info.  If the @APICommand annotation
provides no ACL info, use that.