* Rename OnScreenGui module to ImGui
* Support multiple external module folders (closes#31)
* Cleaning up CMake files
* Restructure application specification
* Add parameter for library mode to all modules
* Add functions to handle global variable state
* Misc/remove warnings (#383)
* Increase build timeout and do a clean rebuild every commit
- Change Time class to become a non-singleton
- Move ownership of the current time to TimeManager(instead of singleton access).
- Store the Time as a Syncable in TimeManager instead of representing all member variables of Time as Syncables.
- Pass a Time object around in the update/render methods, so that renderables don't have to query the OpenSpaceEngine to know if time is paused or if it jumped.
- Introduce Timeline and Keyframe classes
- Make use of Timelineand Keyframeclasses in KeyframeInteractionMode and TimeManager
- Added basic unit tests for Timelineand Keyframe
Future work: Add interpolation schemes for keyframes. Possibly use keyframes+interpolation feature to tween/morph properties, or figure out if this should be a separate mechanism.
