Add support for negative requirements

This change adds support for false matching of requirements. To make
this useful you can now require all approvals match a requirement or
only one (ie any).

Therefore depreciate require-approvals, replacing with
require-approvals-any and a new require-approvals-all.

Change-Id: I458e677315ccb90d64cd0c0e734951141324a9c3
diff --git a/tests/fixtures/layout-requirement-negative-username.yaml b/tests/fixtures/layout-requirement-negative-username.yaml
new file mode 100644
index 0000000..f542b86
--- /dev/null
+++ b/tests/fixtures/layout-requirement-negative-username.yaml
@@ -0,0 +1,37 @@
+pipelines:
+  - name: pipeline
+    manager: IndependentPipelineManager
+    require:
+      all-approvals:
+        - username: '!jenkins'
+    trigger:
+      gerrit:
+        - event: comment-added
+    success:
+      gerrit:
+        verified: 1
+    failure:
+      gerrit:
+        verified: -1
+
+  - name: trigger
+    manager: IndependentPipelineManager
+    trigger:
+      gerrit:
+        - event: comment-added
+          require-all-approvals:
+            - username: '!jenkins'
+    success:
+      gerrit:
+        verified: 1
+    failure:
+      gerrit:
+        verified: -1
+
+projects:
+  - name: org/project1
+    pipeline:
+      - project1-pipeline
+  - name: org/project2
+    trigger:
+      - project2-trigger
\ No newline at end of file