[NUI] Re-design theme resource structure from the tizen-theme-manager (#2633)

[NUI] Re-design theme resource structure from the tizen-theme-manager (#2633)

* [NUI] Fix Selector bug and code by throwing proper exception.

* Fix multiple items bug
* Throw proper exception

Signed-off-by: Jiyun Yang <ji.yang@samsung.com>
* [NUI] Add Theme.Version and improve GetStyle API

Signed-off-by: Jiyun Yang <ji.yang@samsung.com>
* [NUI] Remove build warning and move IThemeCreator to the new file from the ThemeManager

Signed-off-by: Jiyun Yang <ji.yang@samsung.com>
* [NUI] Re-design theme resource structure from the tizen-theme-manager

This patch fixes problem that
the data from the tizen-theme-manager was not able to express mutually exclusive style properties,
such as, BackgroundColor and BackgroundImage.

* IExternalTheme
  * The wrapper interface to express external theme such as Tizen.Applications.ThemeManager.Theme.
  * TizenExternalTheme : Wrapped Tizen.Applications.ThemeManager.Theme.
  * DictionaryExternalTheme : Wrapped Dicrionary<stirng, string>. (for testing)
* ExternalKeyList
  * This class defines a set of keys used in external theme syntax.
  * A set of ExternalKeyList is held by a ThemeCreator in each package.

Signed-off-by: Jiyun Yang <ji.yang@samsung.com>
* [NUI] Fix CornerRadius Policy not applied issue

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