first cut at a gui

use seesaw and core.async to wire up gui
simplify path textfield handling
store previously used directories in local preferences
rename frame
rename frame
gui should already start with correct source and target directories

start refactoring the event handling
switch watcher wrapper to one that supports removing watchers

redirect output to log atom
Merge branch 'gui' of github.com:mhaemmerle/excel-to-json into gui

Conflicts:
	src/excel_to_json/gui.clj
variables should have descriptive names
fix wrong type hint
fix typo in function name
window should have a greater size
rename -dir to -path
move gui main function to respective namespace
highlight actual dynamic items
break long line
Merge branch 'gui'
document running of the gui version
fix spelling
remove jvm headless option