Prefer Communicator constructor over initialize

[bernardnormier]

Like for createProperties vs the Properties constructor, we should offer and prefer Communicator construction over Ice.Util.initialize in some languages, starting with:

• C#
  The syntax is more natural in C# and this enables the CA2000 code analyzer check (make sure you dispose your communicator).

• Java
  Similar to C#, minus the code analysis.

• MATLAB (already done)

[pepone]

We should fix JavaScript too:

• The TypeScript definition declares communicator as an interface, it should be a class.
• You cannot pass the args directly to the communicator constructor, it only takes init-data.