Settings are not applied if set before an url is loaded

Settings are not applied if set before an url is loaded

When applying settings (for example by calling
ewk_settings_scripts_window_open_set) before an url has been set, the
settings are not applied. This is because RenderView has not been
created in the render process. And therefore, the ipc messages are not
catched.

This patch fixes the problem by using using a set of delayed messages in
EWebView. Those messages will be send once RenderView is created.

ewk_view_mode_set also has the same issue, and the patch fixes the
problem.

Some actions do not make sense if no url is loaded (for example setting
scroll position). For some other actions, I don't have an opinion at the
moment (for example setting scale).

Change-Id: I4940d25a998c3f1bd7d940285a851dbd645e27bf
Signed-off-by: Arnaud Renevier <a.renevier@samsung.com>