added more shims, and more extras.

Added ES6 shims for String ...
* contains
* repeat
* startsWith
* endWith
* toArray

Extras for ...
* String.lastSplit
changed some uses of 'indexOf', to 'contains'.

Many uses of 'indexOf' were really interested
in checking if a string was present.

So I have changed those sections, to use the new
ES6 shim, for contains.