FormCommandlineHelp: clarify help text; for dialog: set minimum size, disable maximize box
update merge help images: make conflicts labels smaller, add branch names (current, other), show merge commit above current branch commits instead of other.
help images: branch name get the gray background (instead of the conflicts hint)
small fix
Merge pull request #1539 from feinstaub/topic_helpimages2

update merge help images
Merge pull request #1538 from feinstaub/topic_formcommandline

FormCommandlineHelp: clarify help text; for dialog: set minimum size, disable maximize box