to jdt.core.manipulation

This is one of the series commits to move Templates related code from
jdt.ui to jdt.core.manipulation.

For more information, please check https://bugs.eclipse.org/549989

Change-Id: Ie47b32f07261e008fd45c2d7f73592ac73bdc2c6
Signed-off-by: Sheng Chen <sheche@microsoft.com>