using subprojects to get a portable core
move FileHandling to core and separate IO
move markup to html conversion to core
big/ugly but working/tested implementation of ask-save-on-modify feature
refactorings

- removed the core Actions trait and moved its members to Client
- convert again uses side effects
- core base Client no longer handles files but can via mixin
refactored file handling
Merge branch 'wip-ask-save-on-modify' into develop