Add DALI_COMPOSE_SHADER macro to write shader source conveniently.

Add DALI_COMPOSE_SHADER macro to write shader source conveniently.

[Issue]    N/A
[Problem]  We normally use double quotation marks to write a string such as "Hello World".
           However many symbols are needed to add multiple lines of string.
[Cause]    We don't want to write quotation marks at every line.
[Solution] Add DALI_COMPOSE_SHADER macro to write shader source conveniently.

Signed-off-by: Paul Wisbey <p.wisbey@samsung.com>
Change-Id: I4862e9723a9b16a591385d0f6dd25b5fbbe96b67