doc: Added development notes and minor fixes
doc: Added development notes and minor fixes

Added a new section called "Development Notes" with information about our development process and branch model.

Fixed some minor spelling error and aligned the lines (---) under each heading with their length.

Signed-off-by: Sebastian Niemann <c15bc648238b8fcefd2112b1efddcb822e686c46@sra.uni-hannover.de>
SebastianNiemann/Mantella,Mantella/Mantella,Mantella/Mantella,SebastianNiemann/Mantella,Mantella/Mantella,SebastianNiemann/Mantella