Fix documentation in device interfaces and avoid unnecessary memory allocation in AnalogWrapper

PR of fixes for two annoying things:
* currently AnalogWrapper require the attached IAnalogSensor to resize at each read the Vector passed as an argument to the read() method. This produce an annoying warning in some implementation of the IAnalogSensor, and can be avoided by using a class attribute Vector instead of a local variable.
* a lot of device interfaces are not using the right style for doxygen comment blocks, resulting in broken online documentation ( for instance: http://wiki.icub.org/yarpdoc/classyarp_1_1dev_1_1IAnalogSensor.html ).