Add asbuild utility, update asinit to use it

[jhwgh1968]

At a high level, this separates out invocation of asc from npm (and several quirks related to targets passing arguments) by creating a new command: asbuild.

It supports explicitly passing flags to asc, but mainly focuses on build profiles, each of which corresponds to a certain set of flags. These profiles can easily be added or updated by updating a JSON file.

Usage examples:

asbuild  # runs a debug build
asbuild --release  # runs a build with maximum optimization
asbuild --relmin  # runs a build that is optimized for size
asbuild --debug --release  # runs both a debug and a release build

This new tool uses existing command-line parsing, does not add any dependencies, and allows explicitly specifying output file names the same way that asc does.

This completes the work started in #975, and incorporates all feedback from that discussion.

[dcodeIO]

Has taken me a while to get back to this issue, sorry. While I believe we need something better here, and this is going into the right direction, I am uncertain whether we have pinpointed the optimal solution yet. The new asconfig efforts highlight some of the potential conflicts in that their extends mechanism would cover AS-provided presets, and their targets mechanism would allow multiple targets with slightly varying config options. Like, in a world with asconfig, I'd imagine asbuild to become a more convenient shorthand for asc --config asbuild.json --target something, i.e. asbuild something, so I have been wondering if both efforts can be combined?

[jhwgh1968]

Ah, there is another effort on this front since I opened this!

I will post a comment over on #1230.