Check trailing semicolon for @extend and @include

We weren't checking that uses of `@extend` and `@include` had trailing
semicolons. Add support to the TrailingSemicolonAfterPropertyValue
linter, which will be renamed in a follow-up commit to reflect its new
behavior.

Change-Id: I7a3dd7177cb285952309d14c136fc078f9f6ecb1
Reviewed-on: http://gerrit.causes.com/40961
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane.dasilva@brigade.com>
Rename TrailingSemicolonAfterPropertyValue to TrailingSemicolon

Now that this linter checks more than just property values for trailing
semicolons, its name should be made more general.

Change-Id: I02c4e61d4638741ed707606bb8593d7721ef5147
Reviewed-on: http://gerrit.causes.com/40962
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane.dasilva@brigade.com>
Check variable declarations for trailing semicolon

Change-Id: I227ca13484e4c138c3568af36aa3ccffd4884192
Reviewed-on: http://gerrit.causes.com/40963
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane.dasilva@brigade.com>