More Epiphany string changes

[Michael Catanzaro <mcatanzaro gnome org>]

Hi translators,

I made some more changes to some strings in Epiphany. To the continue
button on network error pages:

"Try Again" and "Reload Anyway" -> "Reload"

And the continue button on TLS error pages:

"Load Anyway" -> "Accept Risk"

I added gettext contexts for the access keys on these pages (which are
translated separately as it's an HTML button rather than GTK+; note
that there's currently no way I could find to display the access keys
but they do work).

A new string "Welcome to Web" appears when you open the browser for the
first time. And since I was making all the changes above, I also
modified the string "Start browsing and your most-visited sites will
appear here" to add a period at the end.

Sorry for the churn so soon before string freeze, and thanks for
updating your translations.

Michael