fix compilation errors and warnings

Xcode was complaining when messages were sent before the method were declared
(most often refresh) => add JBARefreshable protocol to internal interfaces to
fix the errors
* fix some warnings due to incorrect type conversion
* add .gitignore with common OSX & Xcode stuff
Merge pull request #1 from jmesnil/compilation_errors

fix compilation errors and warnings
update sources with license header, added file to include list of contributors
github README markup
replace IBAction with void for consistency across sources
nil out image for non XA-DataSources to prevent re-use from cache
image name fix for add
remove bogus percent calculation in "number-of-resource-rollbacks"
updated jsonkit library that fixes false warnings at compile time
small comment update
fix compiler warning
remove unneeded boolean check
remove unneeded comment.
fix bogus comment.
better orientation support for iOS 5/6
iphone 5 support.
updated project settings.