Extract Style Refactoring

Extract Style Refactoring

Adds a new refactoring, "Extract Style", which will show the user the
attributes for the current selected elements (or if invoked from an
editor context, the attributes overlapping the current caret or editor
selection). The user can select which attributes to extract, and these
are then added as a new style in the styles.xml file in the project
(which is created if necessary). The user can optionally replace the
attributes that were extracted, and the user can also optionally set
the style attribute on the elements to the new style. (Both are on by
default.) This is integrated with the refactoring quick assistant as
well.

Change-Id: I0504e86a824b00730482607150a879ff28233618