media player : handle video filter's state properly

Those changes provide an alternate/better way to handle video filter's state

They'll help to provide another fix for vlc-ios#1240 (closed)

A new object is available as a single instance accessor in the media player class to control the filter It encapsulate :

• all filter parameters' value, default value and allowed values range
• an accessor to enable/disable the filter
• an accessor to apply parameters from another filter
• an accessor to reset the parameters if needed

Former filter accessors are using this new object and are still functional, but they should be avoided and are now marked as deprecated