start replacing the Orocos namespace by OroGen
doc fix
introduction of a separate loading infrastructure, as well as Spec::Typekit and Spec::Project

This moves the loading code outside the Project class, which will
in the end allow to cleanup Project quite significantly in a very
incremental way. The loading mechanisms now create Spec::Project
and Spec::Typekit objects, that are not polluted with knowledge
about the code generation engine.
implement recursive loading of dependencies
loaders: documentation
test: create a clean OroGen::SelfTest module
loaders: separate the loading of textual model representation from the creation of model objects
loaders: cache the set of already loaded projects/typekits in Loaders::Base
loaders: register the set of task models loaded so far
loaders: allow to specify which loader should be used to resolve dependencies
loaders: fix call to __eval__
loaders: fix Project
loaders: move documentation for common methods from PkgConfig to Base
use Project#default_task_superclass to initialize superclass on new task contexts
loaders: get to load the models for RTT/OCL and a test project
loaders: make the set of default typekits an attribute on Loaders::Base
loaders: in pkg-config, workaround bug in oroGen in which it was installing the pkg-config file for non-installable deployments
shuffle code between the Spec and Gen parts
loaders: make it load even more of the Rock orogen projects
test: add tests for Loaders::Base