added some new functions to the turtle API

- turtle/APIs/trt
* combined detectmap and digmap to domap
* added function: opposite
* added function: detect
* added function: digLine
* added function: digPlane
* added function: place
* added function: placeLine
* added return values to all functions indicating the execution status

- turtle/startup
* do-command now only executes the first command in the string
* do-command now returns the return value from the command ;)