main-page-sequence: update the tooltip when the machine got renamed
main-page-sequence: move var down to usage
machine: fix typos and copy'n'paste
machine: add "pretty-name" property

The property will contain the original name if the machine was renamed. E.g.
when using the 'hihat' preset from simsyn and thus naming the machine 'hihats',
the 'pretty-name' will be 'hihats (simsyn)'. This can be used for e.g. tooltips.

See issue #32
machine-preferences-dialog: remove commented code