Added global context
Merge pull request #410 from TheNeikos/add-global_context

Added global context
Add command for overriding a stack position
Merge pull request #413 from matthiasbeyer/add-command_store

Add command for storing a value on a stack position
Fix: Add missing CMakeLists.txt entry for control command source file
Merge pull request #415 from matthiasbeyer/fix-missing_cmakelists_entry

Someone missed to add the CMakeLists.txt entry for the control.c file.
Add convenience function for unblocking a `ws_connbuf`
Use unblocking function in ws_connbuf itself
Use new convenience function in connector
Added exit function to global context
Add context to action manager
Pass context to transactions being run
Merge pull request #416 from TheNeikos/add-cleanup_fn_global_contet

Added exit function to global context
Add CMake module for finding the GBM library
Use GBM in build env
Add GBM device member to framebuffer device
Add EGLDisplay member to framebuffer device
Merge pull request #417 from neithernut/add-action_manager-global_context_usage

Add global context usage to action manage
Add initial, basic egl buffer type
Add pop command