docs/ipc: use an actual event type (thanks Adaephon)
Include workspace con in workspace event

Send the affected workspace in the "current" property for each workspace
event for any type of workspace event that affects a particular
workspace.

fixes #1411
Fix start_application() doc about which shell is used

Since this commit:

f691a55923850a4d315450925fc98733d07b69c9

the shell that is used is the system's bourne shell (/bin/sh) and the
env variable SHELL is not considered.

No logic changes.