#101 Provide a method of getting a task handle by its task name

[Marco Paland]

Provide and implement the following method:

TaskHandle_t xTaskGetTaskHandle(const char* TaskName);

to get a certain task handle by the task name.

In our system we want to use the task notification functions which need a task handle.
We are using c++ task classes and the according task handle is private.
It would be really handy to get the task handle of another task by its (well known) name.

[Marco Paland]

This function has been added in 9.0.0. Thanks A LOT!!
I can remove my own implementation now. Very helpful!