Schedule instantiation

When a rendering is active instantiation will not happen right away.
but it will be scheduled. Currently it is possible to instantiate
only an assembly and an object.

This commit fixes issue #327
Fixed mplay tile callback on OSX.
Fixed bug when entering values lower than the min for sliders
Merge pull request #362 from vidarn/master

Fixed bug when entering values lower than the minimum for sliders
Schedule instantiation: coding style fixes

A few thinkg overlooked in the previous commit.
Merge pull request #360 from marius-avram/B327

Schedule instantiation
Add UI button to reset zoom to 1:1:
- create button and icon
- maintain reset zoom independant for each tab
- attach shorcut to button (removed from widgetzoomhandler)
fix #322
Merge branch 'master' of github.com:nullas/appleseed
minor tweaks
- wrong tweak reveret back
-clean some typo issues
Removed unused UI elements.
Redundant newline
Merge pull request #375 from jammm/master

Removed unused UI elements. Issue #367
fix #322. Test whether pointer return by malloc is 16-bit aligned
fix #322. Romove unused header file
fix #322. Stick to the code style.
fix #332. Stick to the coding style
Merge branch 'master' of github.com:nullas/appleseed