Rename package and modules

[uwefladrich]

PEP8 says about module names:

Modules should have short, all-lowercase names. Underscores can be used in the module name if it improves readability. Python packages should also have short, all-lowercase names, although the use of underscores is discouraged.

which seems to be translated into:

• Package names should have dashes not underscores.
• Module names must not have dashes and can have underscores.

Hence, the proposal is to rename

• the package to scriptengine-ece
• the module to scriptengine_ece

This is also related to uwefladrich/scriptengine#20, which drops the need for implementing SE tasks as namespace packages.

[uwefladrich]

I have made corresponding changes to the scriptengine-hpc package, se uwefladrich/scriptengine-tasks-hpc#3 and the related commit.