Mathieu Servillat / ctools

…lementing missing information from user parameters.

Before, if the output file existed, ctskymap appended an extension to this file.

…ag in the execute() method.

The publish parameter has been added to the following tools:
- ctbin
- ctbkgcube
- ctcubemask
- ctexpcube
- ctmodel
- ctskymap
- cttsmap

Although the get_obs() method was put back, ctmodel used the dummy cube (which consisted of a single pixel) instead of a cube defined from the input parameters. This was due to an internal change of the logic, that now has been corrected for.