Fix hook order

This PR fixes a number of bugs related to the order of hook executions.

1. `jedi:server-args` is not set up before `jedi:setup` because the mode local hook is run after `jedi:setup`.
2. Fixes the bug where the second call to `jedi:setup` from inside the hack local vars hook has no effect because `jedi` pools the epc processes for the same command. Since `jedi:setup` has already setup the process when `python-mode-hook` is called, the second call will have no effect unless you stop the process and make a new one, but that will leave a lingering epc process handle in the jedi server pool table. This PR makes sure only one jedi server process is created per virtualenv.

This PR also renames `pungi-local-variables-hook` to `pungi-setup-jedi` and refactored the code and docs a bit.