Make it possible to launch and track individual Janitor tasks

For now we keep the 'akonadictl fsck' and 'akonadictl vacuum' commands
to execute certain checks in a batch, but we also introduce two new
'akonadictl check' and 'akonadictl migrate' commands. Just used like
this they list all available tasks.
2 jobs for !11 with work/interactive-janitor in 58 minutes and 47 seconds (queued for 1 second)
latest detached
Status Job ID Name Coverage
  Build
passed #53441
build_clazy_clang_tidy

00:58:46

passed #53440
linux kf5-qt5 qt5.12

00:23:10

1.0%