Add base container definitions

This adds the definitions for building the container tarballs for
the base container, the minimal base container, and the toolbox
container.

tmt/plans/container/base/build-generic-minimal.fmf

@@ -0,0 +1,8 @@
+summary: Build Minimal Generic base container image
+discover:
+    how: fmf
+environment:
+    image_type: tbz
+    image_profile: Container-Base-Generic-Minimal
+execute:
+    how: tmt

tmt/plans/container/base/build-generic.fmf

@@ -0,0 +1,8 @@
+summary: Build Generic base container image
+discover:
+    how: fmf
+environment:
+    image_type: tbz
+    image_profile: Container-Base-Generic
+execute:
+    how: tmt

tmt/plans/container/toolbox/build-toolbox.fmf

@@ -0,0 +1,8 @@
+summary: Build Toolbox container image
+discover:
+    how: fmf
+environment:
+    image_type: tbz
+    image_profile: Container-Toolbox
+execute:
+    how: tmt