Customisation feature

#8902 (closed) Add 'custom' flavour
#8905 (closed) Change app name
#8906 (closed) Change package name
#8898 (closed) Change the background image of the main screen
#8900 (closed) Change Navigation Drawer Header
#8899 (closed) Change Splash Screen Design
#8897 (closed) Change theme (for colors)
#8904 (closed) Change launcher icon