CLI Commands: usability improvements

[natemcmaster]

Some ideas for improving the usability of dotnet ef.

• dotnet ef database update doesn't list the migrations being applied/reverted
• Don't require building to get output of --help. We can show help dialog without dispatching to inside-man.
• Support --json on all subcommands
• Allow top-level arguments in any order. E.g. currently dotnet ef dbcontext list --no-build throws, but dotnet ef --no-build dbcontext list works. Part of this is just the way that Microsoft.Extensions.CommandLineUtils works. Command line utils: allow 'inherited' options extensions#131. We still can't completely do this with the way we invoke ef.exe from dotnet-ef.dll.
• Depending on the outcome of https://github.com/dotnet/cli/issues/2514, we may be able to remove "inside-man" dispatch for RTM. NVM. We've pivoted away from ProjectDependencyCommandFactory to our own thing.
• Depending on the resolution to https://github.com/dotnet/cli/issues/2645, we may need to change Ms.EfCore.Tools to also target class libraries. (Support this by cross-compiling the library to netstandard1.5) tracked here: Tools: Support .NET Core Class Library projects #5320
• Help dialog should show options top-level args (--framework) even when listing args for subcommands. Fixed in CommandLineUtils.

[natemcmaster]

We should do this but it can be post RTM.

[VanKichline]

Note that new preview 2 web application templates use 'dotnet bundle' command, so asking for 'dotnet help ef' runs the bundler/minifier and may modify the contents of the project.

[natemcmaster]

@VanKichline you can workaround with the --no-build parameter. e.g.:

dotnet ef --no-build --help
dotnet ef --no-build migrations list 
# etc...

[bricelam]

Closing. Filed remaining work as #6592 and #6593.