I added support for hiding the Close Tab Button.

Hi! I love your Crome Theme plugin! It makes it so easy to configure my Eclipse, that I don't know how I did without it in the past.

In fact, it finally enabled something that I've wanted to do for YEARS, but which Eclipe simply didn't support: hiding the X button on tabs. I alway use the middle mouse button to close tabs, so the X button just got in the way. But with Crome Theme's Custom CSS, I was able to remove it using the "swt-show-close: false" property of CTabItem. So, I figured that it would make sense to add that ability directly to Chrome Theme, so less technical users can take advantage of it.

Unfortunately, I'm not a Java developer, so I don't know how to test the changes I made (I basically just copied the Make MRU Visible option into a new option called Show Tab Close Button). One thing I think may be an issue is that explicitly setting "swt-show-close: true" (When the Show Close Tab Button option is checked) may cause tabs which shouldn't have a close button to suddenly get one. So the CSS generator may need to have some logic in it that only sets the swt-show-close value to false, and skips setting it if it would be set to true. I'm not sure how to actually implement that, though.