Enable dex-preoptimization for overall speedup

Thanks @percy_g2 for the initial commit

PROs:
-- fixes long first boot up times from 10-20min to 4-5min.
-- Later all boots are completed in less than a minute.
-- Overall optimization of dex files of apps and other system files leading to smooth UI and reducing 95% of the lags that were caused.

CONs:
-- Size of the zip goes up by 20-30mb

Performance more important than size zip