WrapInner usage fix

Hello,

I was using your tablesorter plugin and suddenly faced an issue:
One of my columns has button widget in it's head (with sorter:false),
so after applying tablesorter plugin to the table, the data of the button is cleared and I can't disable/enable the button from that moment.

Here is my solution to this problem, but I'm not sure how it will co-work with headerTemplate. Generally it's a bad idea to recreate the content using innerHTML as some widgets can be already initialized there.
If you help me understand the cases where headerTemplate is used, I can complete the solution to be not a breaking change.
Thank you

Short commit history:
- Replace usage of innerHtml with wrapInner to save existing widgets data