Make max concurrent downloads configurable.
Use UIImage.FromFile instead of reading from the file store into memory because it's faster.
Fixed binding bug:

Object type System.DateTime cannot be converted to target type:
MonoTouch.Foundation.NSDate
PictureChooser added - fixes #710
Remove incorrect event reflection - fixes #707
Merge pull request #705 from Costo/uidatepickertimetargetbinding-bug

Fixed binding bug in MvxUIDatePickerTimeTargetBinding
Changes to allow CommandParameter to operate in Tibet style
Merge branch 'v3.1' of github.com:slodge/MvvmCross into v3.1
Merge pull request #691 from ddunkin/v3.1

Performance improvements for DownloadCache plugin.
Merge branch 'v3.1' of github.com:slodge/MvvmCross into v3.1
Follow ups to #691
Additional methods added - addresses #689
Button states - fixes #688
More color converters - Fixes #682
Extra trace - fixes #649