fix string size declaration in orocos.tlb

We want to declare that the type is defined, but the size is
architecture-dependent. Setting to zero makes sure that the local
size is picked.
Revert unnecessary addition of type to orocos.tlb

Otherwise, the explicit definition of types in orocos.tlb would make this file
architecture specific.
Fix input port initializer and integration in TaskContext to take options
Disambiguate orogen generated ros package name from 'native' ros generated
packages

Previously, base/orogen/std would generated a std_msgs package which conflicts
will the existing ros package. Current scheme will now generate a package named
orogen_std_msgs.