[docker] Update GCC and Conan version

[uilianries]

• Use docker image conanio/gcc11-ubuntu16.04:1.48.1
• Update from GCC7 to GCC10
• Update from Conan 1.43.1 to 1.48.1
• Update Artifactory 7.11.5 to 7.38.10
• Remove Travis CI support (it's no longer free)
• Added Github Actions support

closes #96 closes #98

[uilianries]

The images are working, just need to validate it first. I'll test it on my Linux machine (BTW I use Arch).

[uilianries]

@memsharded All good now. We can check the exercise status directly from CI.

Please, note that I updated more things (all listed in PR description)

For now is running on my fork, but after merging it, it will run here too.

Current current is good: https://github.com/uilianries/conan-training/runs/6558999851?check_suite_focus=true

[uilianries]

Downgraded to GCC10 after some tests. The profile expected for Boost 1.72.0 is not available with GCC11 (it's expected as we avoid building old package versions).

Zlib will be 1.2.12 in some cases, but when it's a dependency, not the main package.

https://github.com/uilianries/conan-training/runs/6561117002?check_suite_focus=true

[uilianries]

The curse of git --all ... I gonna revert those changes, sorry.

[uilianries]

Good to go!

The tests now are running into the training docker image.

https://github.com/uilianries/conan-training/runs/6570231090?check_suite_focus=true

[memsharded]

Added some notes in the Academy course, hopefully those comments will avoid some support questions