Rename exercises dir

Name it instead "topics" so it won't be
strange if some topics included "exercises" directory.

topics/aws/exercises/hello_function/exercise.md

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+## Hello Function
+
+Create a basic AWS Lambda function that when given a name, will return "Hello <NAME>"

topics/aws/exercises/hello_function/solution.md

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+## Hello Function - Solution
+
+### Exercise
+
+Create a basic AWS Lambda function that when given a name, will return "Hello <NAME>"
+
+### Solution
+
+#### Define a function
+
+1. Go to Lambda console panel and click on `Create function`
+  1. Give the function a name like `BasicFunction`
+  2. Select `Python3` runtime
+  3. Now to handle function's permissions, we can attach IAM role to our function either by setting a role or creating a new role. I selected "Create a new role from AWS policy templates"
+  4. In "Policy Templates" select "Simple Microservice Permissions"
+
+1. Next, you should see a text editor where you will insert a code similar to the following
+
+#### Function's code
+```
+import json
+
+
+def lambda_handler(event, context):
+    firstName = event['name']
+    return 'Hello ' + firstName
+```
+2. Click on "Create Function"
+
+#### Define a test
+
+1. Now let's test the function. Click on "Test".
+2. Select "Create new test event"
+3. Set the "Event name" to whatever you'd like. For example "TestEvent"
+4. Provide keys to test
+
+```
+{
+  "name": 'Spyro'
+}
+```
+5. Click on "Create"
+
+#### Test the function
+
+1. Choose the test event you've create (`TestEvent`)
+2. Click on the `Test` button
+3. You should see something similar to `Execution result: succeeded`
+4. If you'll go to AWS CloudWatch, you should see a related log stream