Preparations for the 1.0 release

* Less cluttered solution layout.
* Move examples to a repository of its own.
* Move Roslyn analyzer to a repository of its own.
* Enable central package management.
* Clean up csproj files.
* Add README file to NuGet packages.

src/Tests/Spectre.Console.Tests/Expectations/Cli/Parsing/UnknownCommand/Test_1.Output.verified.txt

@@ -0,0 +1,4 @@
+Error: Unknown command 'cat'.
+
+       cat 14
+       ^^^ No such command

src/Tests/Spectre.Console.Tests/Expectations/Cli/Parsing/UnknownCommand/Test_2.Output.verified.txt

@@ -0,0 +1,4 @@
+Error: Unknown command 'other'.
+
+       empty other
+             ^^^^^ No such command

src/Tests/Spectre.Console.Tests/Expectations/Cli/Parsing/UnknownCommand/Test_3.Output.verified.txt

@@ -0,0 +1,4 @@
+Error: Unknown command 'bat'.
+
+       dog bat 14
+           ^^^ Did you mean 'cat'?

src/Tests/Spectre.Console.Tests/Expectations/Cli/Parsing/UnknownCommand/Test_4.Output.verified.txt

@@ -0,0 +1,4 @@
+Error: Unknown command 'bat'.
+
+       bat 14
+       ^^^ Did you mean 'cat'?

src/Tests/Spectre.Console.Tests/Expectations/Cli/Parsing/UnknownCommand/Test_5.Output.verified.txt

@@ -0,0 +1,4 @@
+Error: Unknown command 'bat'.
+
+       bat
+       ^^^ Did you mean 'cat'?

src/Tests/Spectre.Console.Tests/Expectations/Cli/Parsing/UnknownCommand/Test_6.Output.verified.txt

@@ -0,0 +1,4 @@
+Error: Unknown command 'bat'.
+
+       dog bat
+           ^^^ Did you mean 'cat'?

src/Tests/Spectre.Console.Tests/Expectations/Cli/Parsing/UnknownCommand/Test_7.Output.verified.txt

@@ -0,0 +1,4 @@
+Error: Unknown command 'bat'.
+
+       qux bat
+           ^^^ Did you mean 'bar'?

src/Tests/Spectre.Console.Tests/Expectations/Cli/Parsing/UnknownCommand/Test_8.Output.verified.txt

@@ -0,0 +1,4 @@
+Error: Unknown command 'bat'.
+
+       foo qux bat
+               ^^^ Did you mean 'bar'?