Feature autoheight

I added the autoHeight feature (to the best of my belief) which makes the table grow to the size it needs to display all rows at once without scrolling. It grows and shrinks with group expanding / collapsing.

I added the option options.autoHeight to enable it and also added an corresponding example.

https://github.com/globexdesigns/doby-grid/issues/95
No need to submit build/* files in merge requests. These are auto-generated when a new version of Doby Grid is ready to be released.