Merge pull request bolt#1046 from bolt/prepare-rc2

Prepare release Bolt 4.0.0-rc.2

Merge pull request bolt#992 from bolt/bumping-version-number-to-400rc1

Preparing tag 4.0.0 RC 1

Merge pull request bolt#919 from bolt/hotfix/include-composer-package…

…s-in-services

Include Composer packages in ExtensionCompilerPass

Merge pull request bolt#880 from bolt/fix/slug-prefix-on-new-content

Show correct Slug prefix when creating new content

Merge pull request bolt#868 from bolt/updating-packages

Updating packages

Merge pull request bolt#861 from bolt/add-toArray-methods-for-seriali…

…zing-content

add toArray methods for serializing content

Merge pull request bolt#830 from bolt/Use-FilesystemLoader-so-widgets…

…-can-set-the-loader-in-`APP_DEBUG=0`-env-settings

Use "FilesystemLoader" so widgets can set the loader in `APP_DEBUG=0` env settings

Merge pull request bolt#828 from bolt/cleanup-for-logfiles-feature

Some cleanup for logfiles

Merge pull request bolt#825 from bolt/chore/update-npm-deps

Updating NPM deps, and minor tweaks.

Merge pull request bolt#817 from bolt/fine-tuning-buttons

Fine-tuning a bunch of button styles