Small fixes for default text and text without translation

[A.Z.]

Some parts of static text in page files are not translated. For example welcome.html contains "The starting point for your next great Ionic app" that is not added to translate files at all.
Search.html contains ion-searchbar. If placeholder is not defined then English text "Search" is displayed. There are few more places where the text should be translated.
If you agree I can submit pull request to change static text where required and add it to en.json? Others can use this to update the rest of language files accordingly.

[A.Z.]

I see that new pull request that is addressing this issue is submitted 2 hours ago, so this can be closed.