Improve Gitlab-CI configuration

• better use of Gitlab-CI variables
• fix the version of autopep8 to use
• improve usability of generated formatting patch (can be applied with a command using git am)
• add build with gcc 6.2 (C++14), see discussion in !622 (merged)
• run the formatting check only on modified files

Note: this includes !448 (closed)

mentioned in merge request !448 (closed)

• [2018-04-09 17:14] Validation started with lhcb-gaudi-merge#477
• [2018-04-10 00:03] Validation started with lhcb-gaudi-head-py3#119
• [2018-04-10 00:06] Validation started with lhcb-tdr-test#115
• [2018-04-10 00:09] Validation started with lhcb-gaudi-head#1828
• [2018-04-11 00:06] Validation started with lhcb-gaudi-head-py3#120
• [2018-04-11 00:06] Validation started with lhcb-tdr-test#116
• [2018-04-11 00:45] Validation started with lhcb-gaudi-head#1829
• [2018-04-11 01:34] Validation started with lhcb-gaudi-head-py3#120
• [2018-04-11 09:32] Validation started with lhcb-gaudi-head#1829

added 1 commit

• aee28821 - Add build and tests for gcc 6.2 (C++14)

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added 2 commits

• 5b7a6893 - Use new Gitlab artifacts download URL
• 9246b1b6 - Check formatting only on files modified wrt master

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changed the description

added 1 commit

• dbd3ca83 - Check formatting only on files modified wrt master

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added 1 commit

• e38c7667 - Check formatting only on files modified wrt master

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mentioned in merge request !646 (merged)

added 4 commits

• e38c7667...ab1a967b - 3 commits from branch gaudi:master
• 00138145 - Merge branch 'master' into improve-formatting-checks

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approved this merge request

merged

mentioned in commit e1b5afb1

mentioned in merge request !655 (merged)

mentioned in commit e00bb2f2

mentioned in merge request !661 (merged)

added build system label