devtools/madb: default build/install behavior for "start" and "install" commands

"madb install" now builds the project before installing. If the user
wants to skip the build step, "-build" flag can be set to false.

"madb start" now builds the project, and then installs the app to all
the devices before launching the app. The app is newly installed only
if one or more of the following conditions are met:
 - the app is not found on the device
 - the app is outdated (TODO)
 - "-force-install" flag is set

This means that running "madb start" from any Gradle Android project
directory would do the right thing in most cases. Users can still
override the default behavior by configuring the "-build" and
"-force-install" flags.

Change-Id: I86d7002bfd15aef4a15e57bea0991fbdda44fc37
6 files changed