w2grid: add option to *not* mark search results

Marking search results is a nice feature for textual data, but when filtering your records for numerical data it is very annoying to e.g. have all 2's marked in every other column, too.

This proposal adds the option `markSearchResults` to w2grid. It defaults to `true`, so the default behaviour does not change.
Merge pull request #230 from entebaer/patch-4

w2grid: add option to *not* mark search results
Fixed grid.getSelection()
Improved w2alert() and w2confirm() popups
Small test files updates
Fixed issue 229
Column click and resize events and functions
Fixed select with shift+arrow bug
Fixed issue #228