GetItem endpoint

[yillary]

• [x] GetItemLambda
• [x] GetItemRequest
• [x] GetItemResult
• [x] GetItemActivity
• [x] ItemDao.getItem() passing tests
• [x] .yaml updated for lambda section
• [x] events package updated
• [x] gradle build
• [x] sam build
• [x] table deployed

[yillary]

GetItem Backend done. Now going to switch to a new branch and work on the frontend for GetItem endpoint.