Enable multiple consoles

This CL allows enabling of multiple consoles. The expected format
of "androidboot.console" kernel parameter is a list of available
consoles, as follows:

  androidboot.console=tty0:ttyS0

A service can be mapped to a specific console by providing the
optional argument, IE "tty0", to "console" service attribute as follows:

service fbconsole /system/bin/sh
    class core
    console tty0
    disabled
    user shell
    group shell log readproc
    seclabel u:r:shell:s0

Bug: None
Change-Id: I3f8556425c8651bd121995869700f18b23365d55
Tracked-On: https://jira01.devtools.intel.com/browse/BP-289