Simplify Dependency Management Flags

[ChadKillingsworth]

Currently, we have multiple dependency flags:

Closure

• --manage_closure_dependencies
• --only_closure_dependencies
• --closure_entry_point

CommonJS

• --process_common_js_modules - internally this enables --only_closure_dependencies
• --common_js_entry_point - until Support mixing ES6, CommonJS and goog.module systems #1287 is merged, this only supports a single entry point

ES6

We're missing dependencies flags here. You "can" use the closure flags, but you have to specify your entry points as the normalized module name module$path$file.

I'd like to get this down to a single set of flags that supports all 3.

New Flags Proposal

These flags would replace all of the existing dependency flags mentioned above.

• --process_common_js_modules - this would only enable module rewriting.
• --manage_dependencies - This would have two modes (yet to be named) to allow users to control whether dropMoochers is enabled in DependencyOptions.
• --entry_point - this would use the ES6 and CommonJS file based syntax. For closure, it would use the module import syntax: goog:namespace

[ChadKillingsworth]

For the new --manage_dependencies flag, the options could be STRICT and LOOSE.