Add ability to select tasks to run with live-dev

[s-KaiNet]

Currently live-dev running about 20-30sec. and performs whole build validation (vet, transpile, test, build).
Sometimes some steps might not to be necessary. For example if you developing a new directive, you have tslint plugin and fix all vet errors right in your dev tool, then you probably need only test task, which run quickly, but currently you need to wait the whole validation to finish.
Proposed solution: add ability to select tasks to run, i.e.

gulp live-dev --tasks test serve --specs --dev

This adds flexibility and reduce running time for live-dev.
Currently I'm going to focus on navbar component, if anybody wants to take this one, you can go ahead. Though if this is more important than navbar, I can switched on this temporary, or just shift implementation on a bit later time.

[andrewconnell]

Hey @s-KaiNet I'll take this on... you're more productive doing components than I am, and I'm working on some process stuff for us, so I'll happily work on this. Got some ideas already that I'll share here in an updated spec...

[s-KaiNet]

ok, no pb

[andrewconnell]

I'm going to unassign myself from this... this isn't a small task and I'm working on some higher priority build process stuff for now.

[andrewconnell]

Moving this to the backlog... not critical at this time.