clang-tidy checks:
readability-isolate-declaration and readability-braces-around-statements

KF task: https://phabricator.kde.org/T14729

GIT_SILENT

- Use QString::arg(Args...) instead of .arg().arg()
- Use QLatin1String for string comparisons, should be faster
- Use QLatin1String::arg() for better readability

- Add the comment dfaure suggested in the MR, to explain why it's '2%'
  then '%1' in a QString().arg().arg()

NO_CHANGELOG

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Fix some clazy warnings, and some other minor code optimisations.

NO_CHANGELOG

Summary:
Convert license headers to SPDX statements and add
license files as required by REUSE specification.

Reviewers: cgiboudeaux

Reviewed By: cgiboudeaux

Subscribers: ognarb, cgiboudeaux, kde-frameworks-devel

Tags: #frameworks

Maniphest Tasks: T11550

Differential Revision: https://phabricator.kde.org/D27601

Summary: Add a simple delete option to kwriteconfig. A possible usecase of this option is to delete unused shortcut bindings.

Reviewers: #frameworks, davidre, dfaure, meven, cfeck, davidedmundson

Reviewed By: davidedmundson

Subscribers: davidedmundson, ngraham, kde-frameworks-devel

Tags: #frameworks

Differential Revision: https://phabricator.kde.org/D25307

Summary: compile without foreach

Test Plan: Unittest Ok as previously

Reviewers: dfaure

Reviewed By: dfaure

Subscribers: kde-frameworks-devel

Tags: #frameworks

Differential Revision: https://phabricator.kde.org/D19326