Add some more helpful information to the assertion failure in Clicker.clickOnScreen(float,float).

Include the computed (x, y) coordinates of the faile click, plus the name and message of any SecurityException encountered.
when the Sender cannot complete an action, add information about any possible exception that was responsible.
Hide soft keyboard when dragging
Sleep after hiding the keyboard
Bugfix for issue-497
Added a null check in GLRenderWrapper.
Merge pull request #59 from pererikbergman/master

Added a null check in GLRenderWrapper.
Added clickOnMenuItem(View view)
Modified clickOnMenuItem()
Removed clickOnMenuItem
Bugfix for issue-504
Added the new method getString(String id)
Refactored and improved hideSoftKeyboard()
Added scrollToSide methods with scrollLength parameter
Bugfix for issue-506
Javadoc update in WebElement
Added null check in assertCurrentActivity
Added null check in getNumberOfMatches
Always return the total amount of matches in getNumberOfMatches
Minor javadoc update