added ofEasyCam::updateCam which has the logic of ::update().

- it needs to run at least once, so all variables are initialized (i guess).
extracted code from ofEasyCam::update and placed in a new method ::updateCam.

- this is just a quick fix. needs review.
the updateCam needs to be called in the initialization of the class.
Merge branch 'feature/bugfix-ofEasyCam-disableMouseInput' into develop