added methods to set min&max of a slider
added getter for min&max of ofxSlider
iOS Fixes for #2469 and Device Definitions Update

- Updated Enums to be in correct oF Style.
- Updated Defines to be in correct oF Style.
- Enums now backwards supported for pre-0.8.
- Updated Device definitions with all released iOS Devices

Implemented above fixes as mentioned in #2469
fixes #679

bank = xAxis,heading =  yAxis, attitude = zAxis .
The rotation order is Y,Z,X; OpenFrameworks works in row Major so, the
Quaternion multiplication order is- xRotation * zRotation * yRotation.
added comment to specify rotation order
Merge branch 'master' of github.com:openframeworks/openFrameworks
Const-corrections for ofUtils.
Initial progress on documentation of ofUtils.h.
Typo fixed.
Merge branch 'master' of github.com:openframeworks/openFrameworks into feature-documentation

Conflicts:
	libs/openFrameworks/utils/ofUtils.h
Some typo fixes.
Merge pull request #2911 from openFrameworks-ofFont/feature-ofUtils-const-correction

Const-corrections for ofUtils
Gstreamer stride fix for videos with unusual widths
two small fixes
reverting change
Merge pull request #2921 from pierrep/bugfix-gstreamer-stride

Gstreamer stride fix for videos with unusual widths
changelog for last commit
Merge branch 'master' of github.com:openframeworks/openFrameworks
PG update submodules to last commit
fixed for mouse registration issues with ofxGui.
issues included,
- ofxPanel was registering for mouse events 3 times on setup!
- ofxButton was registering for events in setup and registering again in the destructor.
- ofxSlider was never unregistering mouse events.

added mouse register and unregister methods to ofxBaseGui,
so all classes that extend ofxBaseGui add/remove mouse events via these method.

`registerMouseEvents()` and `unregisterMouseEvents()` have a flag which makes sure that no multiple mouse registration can be made.

`~ofxBaseGui()` destructor now unregisters mouse events for every `ofxBaseGui` object.