feat(library): support a custom data source (aquasecurity#613)

* chore(mod): update trivy-db

* refactor(detector/library): use programming language instead of package
manager

* feat(library): add general advisory

* test(utils): add a util function initializing DB

* test(advisory): add tests

* chore: use aquasecurity/bolt-fixtures

* refactor: add comments

* chore(mod): revert fanal version

* chore(mod): update trivy-db

* refactor: update the comment

Fix comparison table to use words instead of symbols (aquasecurity#587)

fixes aquasecurity#301

Revert Dockerfile changes (aquasecurity#581)

Fix non-root directory permission denied error (aquasecurity#578)

* Fix non-root directory permission denied error

* Updated Readme

* Fixed Readme

* Updated readme to use latest tag for QA error

* updated Dockerfile

* Moved error to others section

Fixing `Error retrieving template from path` when --format is not tem…

…plate but template is provided (aquasecurity#556)

fix(alpine): support 3.12 (aquasecurity#517)

fix(app): add ArgsUsage (aquasecurity#508)

Add image subcommand (aquasecurity#493)

* config_test: Add missing assertions for TestNew

Signed-off-by: Simarpreet Singh <simar@linux.com>

* integration: Add integration tests for image subcommand.

Signed-off-by: Simarpreet Singh <simar@linux.com>

* refactor: bump up urfave/cli to v2.0

* refactor: apply DIY to image flags

* refactor: reorder sub commands

* feat: set hidden to global image options

* test(integration): insert --cache-dir before sub command

* README: update readme to reflect new usage

Signed-off-by: Simarpreet Singh <simar@linux.com>

* chore(README): add image subcommand

* fix(flags): define aliases according to urfave/cli v2.0 style

Co-authored-by: knqyf263 <knqyf263@gmail.com>

chore(ci): move integration tests to GitHub Actions (aquasecurity#485)

* fix(standalone): add defer to close databases

* test(client/server): launch a server only once

* test(docker_engine): remove the duplicated case

* test(docker_engine): copy a database only once

* test(standalone): copy a database only once

* test(server): fix tests according to updated mock

* chore(mod): update

* chore(ci): add integration tests to GitHub Actions

* chore(ci): bump up Go to 1.14

* chore(ci): remove integration tests from CircleCI

* chore(ci): add name

* chore(ci): add new lines

feat(db): store metadata as a file (aquasecurity#464)

* refactor: wrap errors

* feat(db): add the metadata file

* test(db): re-generate mocks

* fix(app): read metadata from the file in showVersion

* fix: open the database after downloading it

* fix(operation): use UpdateMetadata

* chore(mod): update dependency

* test(integration): fix tests

* fix(conf): rename TRIVY_NONSSL to TRIVY_NON_SSL