Using global variable names.
Parameters API doen't have Caches Policies anymore.
Polymorphic_map unused. Deleted.
Subscribe functionality.
The user can subscribe a function when creating the parameter.
ParamterServer handle the callbacks from the server.
Command class.
Commands queue to execute Commands. Is thread safe.
SubscribersManager with test.
Setting Qt Creator
Refactorized Subscribers manager in Parameter Server.
Parameters container stores the parameters values.
Removed commented code.
Saving changes to change the branch.
Created class parameter.
Parameter class.
Parameter server with async spin.
Merge branch 'create_parameter_class'

Conflicts:
	parameter_example/CMakeLists.txt
	parameter_example/include/parameter_server/parameters_server.h
	parameter_example/test/parameters_server_test.cpp
Creating API following the examples of ros_parameter.
Removed qt creator files.