Handle exceptions via stderr & exit code

Currently when you run the console ApiComparer without arguments it'll crash unhandled

Unhandled Exception: System.Exception: No target assemblies specified, please use --source {asm1};{asm2}...
   at Program.GetExplicitAssembliesToCompare(String[] args) in \APIComparer\APIComparer\Program.cs:line 176
   at Program.Main(String[] args) in \APIComparer\APIComparer\Program.cs:line 30

What's proposed in this is PR is

Refactored so exceptions
- Are handled
- Logged to stderr
- Known / Unknown reflected on exit code
Also breaking change reported via exit code

Post this change program crash won't occur, instead "known" exceptions will result in error message being printed to stderr and exit code changed.

Argument exception: No target assemblies specified, please use --source {asm1};{asm2}...

And unhandled exceptions will log exception with stacktrace to stderr and change exit code example:

Unhandled exception: System.IO.FileNotFoundException: Could not load file or assembly 'dll' or one of its dependencies. The system cannot find the file specified.
File name: 'dll' ---> System.IO.FileNotFoundException: The system cannot find the file specified. (Exception from HRESULT: 0x80070002)
   at System.Reflection.AssemblyName.nGetFileInformation(String s)
   at System.Reflection.AssemblyName.GetAssemblyName(String assemblyFile)
   at APIComparer.ComparerEngine.IsManagedAssembly(String assemblyPath) in \APIComparer\APIComparer.Core\ComparerEngine.cs:line 61
   at APIComparer.ComparerEngine.<ReadTypes>b__3_0(String assembly) in \APIComparer\APIComparer.Core\ComparerEngine.cs:line 42
   at System.Linq.Enumerable.WhereListIterator`1.MoveNext()
   at System.Linq.Enumerable.<SelectManyIterator>d__16`2.MoveNext()
   at APIComparer.CecilExtensions.RealTypes(IEnumerable`1 types) in \APIComparer\APIComparer.Core\CecilExtensions.cs:line 159
   at APIComparer.ComparerEngine.CreateDiff(IEnumerable`1 left, IEnumerable`1 right) in \APIComparer\APIComparer.Core\ComparerEngine.cs:line 77
   at APIComparer.ComparerEngine.CreateDiff(AssemblyGroup leftAssemblyGroup, AssemblyGroup rightAssemblyGroup) in \APIComparer\APIComparer.Core\ComparerEngine.cs:line 31
   at Program.Compare(CompareSet compareSet, Boolean showAllVersions) in \APIComparer\APIComparer\Program.cs:line 65
   at Program.<>c__DisplayClass0_0.<Main>b__0(CompareSet set) in \APIComparer\APIComparer\Program.cs:line 38
   at System.Linq.Enumerable.All[TSource](IEnumerable`1 source, Func`2 predicate)
   at Program.Main(String[] args) in \APIComparer\APIComparer\Program.cs:line 38`

Also did a small optimization, previously --show-failed-only was parsed each iteration, it's now parsed only once.

andreasohlund / APIComparer

Handle exceptions via stderr & exit code #66