Add support for peers names as string variables

[ahoarau]

This PR allows to write scripts as :

var string comp_name = "hello"
loadComponent(comp_name,"OCL::HelloWorld")
comp_name.configure()
comp_name.start()

The commented cout returns : Peer as string variable comp_name --> hello

[meyerj]

See also my comment in #149 (comment) with an alternative proposal to solve the problem.

I do not like the implicit conversion from string variables to a peer very much and would suggest the opposite approach, namely to return a TaskContext * from loadComponent(). As a result, your example would have to be written like

var string comp_name = "hello"
var TaskContext comp = loadComponent(comp_name,"OCL::HelloWorld")
comp.configure()
comp.start()

with a clear separation between the actual component (comp) and its name (comp_name). Additionally, each TaskContext could expose getPeer(string name) as an operation to convert from names to actual TaskContext instances explicitly.

Implicit conversion from TaskContext to string or vice-versa as originally proposed in #149 (comment) might not even be required if the PeerParser handles variables of type TaskContext in the same way as peers, so that names of peers and variables pointing to TaskContexts can be used interchangeably in scripting.