WICKET-4941 Component.initModel() does not cause parent models to be initialized

(cherry picked from commit 7042f88549f9f14e89ad7a37916ab17470f8e5ac)
Non-functional changes

Minor fixes in comments
Calculate local variable just once
Append char instead of String when possible

(cherry picked from commit 7b0d8ea0c981d6cdff2a12f5b7317f7170ecec43)