build.sh: add timestamp to build-logs

Read commit description from kitkat branch.
build.sh: fix derpt
Update our ROM version name

-Use PA version instead, so it wont confuse the users
-Keep PSD_VERSION for "ParanoidSaberDroid Version" in About Device settings
-And also, keep "psd_" and "REMIX" name there
We still need CUSTOM_TARGET_PACKAGE, or else it will not show the version on zip files (2/2)
Show the date, and use the PSD_BUILD_NAME for modversion as well