[*] StbMainApp: Apply patch from GARB. Improve usability of switching dvb channels.

Changes:
 * On DVB channel change watched channel is saved
 * While in play control press 0 remote button to jump to previous watched channel
 * While in play control up and down arrow remote buttons display channel list

Signed-off-by: Anton Sergeev <Anton.Sergeev@elecard.ru>