Change the way how python program URLs and read-only Python code is handled

[johann-petrak]

See discussion in #33

What we want:

• get rid of working dir and python program path parameters, only keep the python program (URL) parameter
• only support file URLs and jar URLs
• if file URL, enable the editor and run as a python program file
• if jar URL, disable the editor and run as a python module

We should probably also check if a file: file is writable and not allow the editor if it is not.

[johann-petrak]

Branch issue35

[johann-petrak]

This is not trivial: there are, in theory two ways how to run a python program from inside a zip/jar:

• a) put the zip on the pythonpath and load it as a module using python -m modulename: in that case, the modulename must not start with a slash and must not have the ending .py extension. Also the code must not check for name "main".
• b) run a directory from within the zip, if there is a file "main.py" in the zip.

Method b) requires a specific name and apparently the way how the program is run is a bit weird since the program is not also loaded as a module.

Method a) requires that some parent directory of the file withiin the zip file is on the PYTHONPATH. This in turn has two possible disadvantages:

• any other directories and files within the zip pythonpath shadow the corresponding files on the system python path.
• if the gatenlp package of the plugin is in that pythonpath, the parameter to use our own wont work

The only way to work around these issues seems to be:

• make sure that the parent of gatenlp in the resources is otherwise empty - put that parent in the PYTHONPATH if we want to use the plugin gatenlp
• always put the containing dir of the python file on the path

[johann-petrak]

Fixed by #36