.pytool/Plugin: Add CI plugins

https://bugzilla.tianocore.org/show_bug.cgi?id=2315

Add .pytool directory to the edk2 repository with the
following plugins.  These plugins are in a top level
directory because that can be used with all packages
and platforms.

* CharEncodingCheck
* CompilerPlugin
* DependencyCheck
* DscCompleteCheck
* GuidCheck
* LibraryClassCheck
* SpellCheck

Cc: Sean Brogan <sean.brogan@microsoft.com>
Cc: Bret Barkelew <Bret.Barkelew@microsoft.com>
Cc: Liming Gao <liming.gao@intel.com>
Signed-off-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

.pytool/Plugin/DscCompleteCheck/Readme.md

@@ -0,0 +1,27 @@
+# Dsc Complete Check Plugin
+
+This CiBuildPlugin scans all INF files from a package and confirms they are
+listed in the package level DSC file. The test considers it an error if any INF
+does not appear in the `Components` section of the package-level DSC (indicating
+that it would not be built if the package were built). This is critical because
+much of the CI infrastructure assumes that all modules will be listed in the DSC
+and compiled.
+
+## Configuration
+
+The plugin has a few configuration options to support the UEFI codebase.
+
+``` yaml
+"DscCompleteCheck": {
+        "DscPath": "",   # Path to dsc from root of package
+        "IgnoreInf": []  # Ignore INF if found in filesystem by not dsc
+    }
+```
+
+### DscPath
+
+Path to DSC to consider platform dsc
+
+### IgnoreInf
+
+Ignore error if Inf file is not listed in DSC file