Implement proper argument parsing

[granicz]

When I run wsfsc.exe without any arguments, I get this non-friendly output:

C:\>wsfsc.exe
WebSharper error FS9001: Global error 'Value cannot be null.↔Parameter name: path1' at    at System.IO.Path.Combine(String path1, String path2)↔   at WebSharper.FSha
rp.Program.compileMain$cont@260(String[] argv, Unit unitVar)↔   at WebSharper.FSharp.Program.main(String[] argv)

This needs to give me a nice argument listing with a version information about the underlying compilers.

[Jand42]

Also:

• Make sure to print argument parsing errors in a clean way (single helpful message, no stack trace)
• If there are no --project arguments specified, look for a single .fsproj/.csproj
• Do not fail on having multiple --ws arguments, use the last one for project type (multiples can happen if a NuGet update does not uninstall Import for targets file correctly.)
• Add --help options to print WebSharper compilation arguments and also unpack/html commands inherited from WebSharper 2/3

[Jand42]

TODO:

• Include used version of Roslyn/FCS in info

[Tarmil]

I'm implementing the Roslyn/FCS info, plus this:

• more consistent syntax for boolean flags: --foo or --foo+ sets to true, --foo- sets to false (like fsc).