[NUI] Fix not to get framework path via StyleManager

[NUI] Fix not to get framework path via StyleManager

StyleManager uses dali singleton service which is not initialized in PreLoad().
Previously in Preload(), ThemeManager got framework resource path via static constant in StyleManager,
which leaded to initialize StyleManager instance that is not valid in PreLoad().

So this patch moved framework resource path constant to the constant file.

Signed-off-by: Jiyun Yang <ji.yang@samsung.com>