travis: more cleanup

[tooomm]

Short roundup of the initial problem

Unneeded package installs listed in travis.yml

What will change with this Pull Request?

• cmake and clang (clang-format is part of it) are already available in the Travis Linux build image:
  https://docs.travis-ci.com/user/build-environment-updates/2017-12-12/#Changed
  The logs now also print their version numbers.
• bc used to be included in the newest version, too
  https://travis-ci.org/Cockatrice/Cockatrice/jobs/405156717#L428
• clang-format is never used on mac builds (we only check on Linux), remove its installation
• Added links to the related build image changelogs for each ci service
• conditions config can be removed as it's the default now
• Add job names
• Remove fast finish, which only has effects when allowed failures are configured

I tried to remove the other apt installs which should be already available in the Xenial image regarding this list: https://packages.ubuntu.com/xenial/allpackages (long load time!)
But it didn't work out. 😃

Screenshots

[ctrlaltca]

If clang-format is already available, you can also remove the lines used to import the apt source for the llvm repository: https://github.com/Cockatrice/Cockatrice/pull/3336/files#diff-354f30a63fb0907d4ad57269548329e3R36
clang-format is a bit picky, since different versions can need different config files and different report errors, so you happen to know what version in installed? Ubuntu should have 6.0-41~exp4 installed by default

[tooomm]

clang-format is a bit picky, since different versions can need different config files and different report errors, so you happen to know what version in installed? Ubuntu should have 6.0-41~exp4 installed by default

clang 5.0.0 is installed (see here), so it's clang-format 5.0.0, too:
https://travis-ci.org/Cockatrice/Cockatrice/jobs/411445789#L2101

I guess you are talking about a newer Ubuntu than the 16.04 Travis still uses. ;P

[ctrlaltca]

Oh, you are right, i always forget how outdated the travis arch is.

[tooomm]

@ctrlaltca Can you revisit and merge this PR, please?

I want no other CI stuff to lie around before looking into further changes.