Fix yamllint issues and make it blocker

All yamllint issues in yaml files have been fixed except line-length rule
which is excluded. tox.ini is updated in order not to ignore yamllint issues
so if yamllint fails, the change will get verified-1 and will be blocked from
merging. yamllint configuration file, .yamllint, is also created to configure
what is enforced.

As a summary, most frequently occurring issues that are fixed are below.
- truthy value: must be true/false and not yes/no
- indentation: blocks are incorrectly indented mostly
- braces: extra spaces after opening and before closing curly braces are not good
- colons: extra spaces after colons - should be single
- missing document start
- comments: there should be a space after hash

Change-Id: I0d1341f2639585228b1ae8fd6ee073e5cae53604
diff --git a/.yamllint b/.yamllint
new file mode 100644
index 0000000..fb924d7
--- /dev/null
+++ b/.yamllint
@@ -0,0 +1,32 @@
+---
+yaml-files:
+  - '*.yaml'
+  - '*.yml'
+  - '.yamllint'
+
+rules:
+  braces: enable
+  brackets: enable
+  colons: enable
+  commas: enable
+  comments:
+    level: warning
+  comments-indentation:
+    level: warning
+  document-end: disable
+  document-start:
+    level: warning
+  empty-lines: enable
+  empty-values: disable
+  hyphens: enable
+  indentation: enable
+  key-duplicates: enable
+  key-ordering: disable
+  line-length: disable
+  new-line-at-end-of-file: enable
+  new-lines: enable
+  octal-values: disable
+  quoted-strings: disable
+  trailing-spaces: enable
+  truthy:
+    level: error