Fix scripts not installed in subfolder 'bin'
task-process: Add property "pid"

Will be set to the PID of the running process when waiting for it.
terminal: Add option cancel_childless

Enabled by default, it will cancel the running task on Enter/Esc if the
running process (i.e. terminal emulator) has no children.

For example after running `df -h` in an embedded terminal, a simple Enter
will close the terminal.
doc: Fix re: new gtk-doc (markdown) syntax
doc: Little fixes/updates