Email composer's caret width should be same as EFL entry

[Title] Email composer's caret width should be same as EFL entry
[Problem] The caret width of the sender field and the body in email composer are different each other.
[Cause] The sender field is implemented with EFL entry and the body is implemented with webview.
        EFL entry's caret width is one pixel but the webview's caret width is 3 pixel.
[Solution] Decide the caret width of the webview according to the environment variable.
Implement about featurs such as 'about:memory'