Add EmptyLineBetweenBlocks linter

Add linter which checks for the existence of a separating blank line
between block definitions.

Closes #63

Change-Id: Ifa5e39a019df477e3b652b25d40a206660767cdf
Reviewed-on: https://gerrit.causes.com/32425
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>