Initial system support

We have to have two primary sides of test framework implemented: router and host.

Generic steps:

• pexpect abstraction for asserts
• targets configuration

Router specific abstractions:

• pexpect console handler
• reboot pin handler
• uboot prompt support
• shell prompt support
• power handler
• post-test shutdown

Host specific abstractions:

• container base system
• container spawner and handler
• pexpect container connection abstraction
• post-test teardown and container lifespan

Integration steps:

• router network boot
• router ISP container
• router device container