IPython Console: Create a new client in a way that the user can get visual feedback while it's created

- Before a new client tab was added only after the kernel was created (which
takes between 4 to 6 secs), and so the user didn't really know what was happening
during that time.
- Now a new tab is added immediately and while we start kernel we show a WebView
widget. This is blank now but the plan is to display a simple animation in it to
to indicate that the client is being created.
Update translations
Update Spanish translation
Update CHANGELOG
Update version
Added tag v2.2.4 for changeset b93cd108d4c7
External Console: Add default option to 'pythonexecutable/custom' while starting an IPython Kernel

- This was generating a traceback if the user was trying to open an IPython
console before opening Preferences.
History Log: Tabify it next to the External Console on first run

Backport of revision db4fea3610b4 (which I forgot to do!)
Added tag v2.2.4 for changeset 7f6dbad547e2
IPython Console: Improve how to set kernel and client tab names for new clients

- The name is set according to the kernel pid, so we now pass it from the
External console (where the kernel is created) to the IPython one.
IPython Console: Refactor "start_new_client" -> "create_new_client"
IPython Console: Fix connection to external kernels, which was broken since revision a6cac2060473
IPython Console: Create shorter names for clients connected to notebook kernels

- Notebooks kernels use uuid's for their id and they are very long.
IPython Console: Fix restarting kernel action which was broken since revision a6cac2060473
IPython Console: Develop a better way to restart kernels

- The idea is to use register_client with a new parameter called 'restart', to
connect the client to a new kernel.
IPython Console: Remove 'restart' parameter introduced in revision a905dace5e59 where it wasn't needed
IPython Console: Remove unneeded paramater "kernel_widget_id" from "register_client"
External Console: Refactor "create_ipyclient" -> "register_ipyclient"
IPython Console: Refactor "create_new_kernel" -> "restart_kernel"
Merge from 2.2 (Update CHANGELOG and fix a bug while starting an IPython Kernel)