Miscellaneous dialog fixes

This fixes a handful of problems with the EWF dialogs that arose during the Brackets Sprint-26 jQuery/LESS/Bootstrap/modal-dialog upgrade. This patch fixes in particular:  

1. the vertical alignment of the modal header titles and close buttons;
2. the font size and color of the code block in the insert dialog;
3. an issue where the entire modal body of the picker dialog was scrollable inside the dialog;
4. the alignment of the font tiles within the picker dialog; 
5. various dialog dismissal bugs, chief of which prevented close icon clicks from dismissing the dialog.