Enable definition of function with the same name than an intrinsic
In operator for sliced_string in string
Add file type information
Improve string interface

* split, startswith and endswith
Make pythran runnable from dev folder

Workflow is really slower when we need to reinstall everything before each test: Pythran should have +x right
Remove obsolete option
Fix several assignment / aliasing issues

Now clearly distinguish between index_ndarray, sliced_ndarray and
gsliced_ndarray.

Use the typing information to perform deep or swallow copy when needed.