init: Create classes for Action and Command

This creates the concept of 'event_trigger' vs 'property_trigger'

Previously these were merged into one, such that 'on property:a=b &&
property:b=c' is triggered when properties a=b and b=c as expected,
however combinations such as 'on early-boot && boot' would trigger
during both early-boot and boot.  Similarly, 'on early-boot &&
property:a=b' would trigger on both early-boot and again when property
a equals b.

The event trigger distinction ensures that the first example fails to
parse and the second example only triggers on early-boot if
property a equals b.

This coalesces Actions with the same triggers into a single Action object

Change-Id: I8f661d96e8a2d40236f252301bfe10979d663ea6