Added tab-completion for yarp rpc when Readline library is available

(only works properly with Thrift-generated services)
When available, use Readline for all stdin operations [thanks Alexis Maldonado for the original patch]
Added proper FindReadline.cmake and use our CMake package-handling macros
yarp companion: Fixed EOF detection
yarp rpc: only ask command list to the server when tab completion is invoked
[thift] add help command itself to the list of commands reported by the default help function
yarp rpc with readline: complete "help a<TAB>" inputs
remove static SystemClock instance, fixes #129

Using a static instance here was lazy and relied on the assumption
that yarp::os::Time would only be used late, after library
initialization.  But existing code (e.g. yarpview) breaks that
assumption.  Thanks @gsaponaro for reporting.
fix Value assignment operator under reassignment, see #128

For v = v2, a pre-existing value in v of a different type to v2
could disrupt the copy.  Thanks @pattacini for reporting.
[Cleanup]
[Manager] Move headers in yarp/manager
[Manager] Move library in yarp/manager C++ namespace
[Manager] Install CMake files

The manager library can now be found (if installed) using

  find_package(YARPManager)

Once found the YARP::YARP_manager target and the
YARP_MANAGER_INCLUDE_DIRS and YARP_MANAGER_LIBRARIES will be available.
give a clearer message when a thread fails to start

fixes #127, thanks @JoErNanO!
Fixed IPositionDirect doxygen documentation
[SERIAL] Removing obsolete parityenb parameter from config file. Cleaning out output messages of device. Return false when device fails read/send operation.
Merge pull request #131 from JoErNanO/master

[SERIAL] Fixing a few issues with the serial device interface.
VirtualAnalogWrapper: fixed map for torso
Merge pull request #124 from elen4/useReadline

Use GNU readline in the yarp companion when available
Merge pull request #130 from drdanz/ymanager_public

Make YARP_manager library public