GitLab

* replace golangci-lint with govet and golint go-task task

going in the direction of removing travis.ci in favour of drone io,
and in order to have a clean linting check output, golangci-lint was
removed because the output for this codebase was too confusing

* refactor task check and add task check-legacy

in order to be aligned with test task style we will have a legacy
(ugly) lint output if requested and meanwhile  we will focus on the
"new refactored part" of the code with lint and fmt to speed up
the development and refactoring

* removed go lint check for legacy lint task

no need to be obsessed on linting for a module that will be properly
refactored out from the legacy

* add dynamic DEFAULT_TARGET generation list

* replace golangci-lint with simple go-task check

* fix upload for integ and unit test in codeconv.io

* raise to 10m test timeput for unit and integ tests

* add task test-unit-race to specificly run unit test with rece condition
detection

in order to do not slow down testing too much also because we do not
have particular race conditions to detect at the moment

* clean from drone configuration and related dockerfiles

* add missing documentation temporary comment to make linter happy

this is a FIXME commit, in next months all the FIXMEDOCS placeholders
must be replaced with proper documentation