added base web view controller,  refactoring
WebViewController navigation, subviews
changes webviewcontroller, loading view controller from root view controller
changes web view scrolling behaviour
fixes hide toolbars/nav. bar while scrolling down
tap gesture for show/hide controls
fixes #252
changes handle navigation + sub views
bug fixes help web view controller
Merge branch 'master' of github.com:Catrobat/Catty into feature/issue#252

Conflicts:
	src/Catty/CatrobatTableViewController.m
fixes scrolling buttons behaviour
Merge pull request #274 from Catrobat/feature/issue#252

HelpViewController issue #252