Prepare next development iteration

Change-Id: I8b2902ade13173a4bf476d9aed6594d3185a1a99
Add model for Mixer element

Change-Id: I87a2c13f0de599d37f7e5efc767e151664ed09ff
Change kurento logo

Change-Id: I61a5e023ddef361588644586b405d4da50462774
Use kms-cmake-utils for common cmake tasks

Change-Id: I5307023eb93c31f4abac6426518d9844046e53cb
Add build directory to .gitignore

Change-Id: Ic00b983dcbd1f95753d654554b721948d90e937b
Make generated code be compatible with jsonrpc library

Change-Id: I7d4e3654060260a630fadbc8be66a09567ef8b4b
Prepare release 4.3.1

Change-Id: I80f01852924e32f83328cb1151d292956480f6ee