Add option to add a split to a song 
This will split the verse when added to the service but keep the verse together for editing.
Useful for the 10 line hymn verses which need 2 slides to display.

Fix some iffy spelling

lp:~trb143/openlp/splitter (revision 2738)
[SUCCESS] https://ci.openlp.io/job/Branch-01-Pull/2182/
[SUCCESS] https://ci.openlp.io/job/Branch-02-Functional-Tests/2085/
[SUCCESS] https://ci.openlp.io/job/Branch-03-Interface-Tests/1972/
[SUCCESS] https://ci.openlp.io/job/Branch...