added updateUrl property to be abble to check for newer add-ons versions
more verbose log to debug update check errors
updateUrl defaults to homepage/version.txt
store the last version of an add-on
added add-ons update check to updater
Renamed "lastVersion" to "latestVersion" and added comments
fixed a switch between two buttons (add-on homepage vs add-on
update-url)
back to unix file format
sync with upstream
Revert "sync with upstream"

This reverts commit 54ab88909248202b0efb41d371a1b97264adccce.
little improvement for OptionPanel.script_directories.tooltip
use the same classloader for all scripting operations (non-Groovy only)
Merge branch 'seb4stien/addon-update-check' of github.com:seb4stien/freeplane into seb4stien-seb4stien/addon-update-check
handling undefined 'homepage' for add-ons
fixed updateUrl attribute name
basic support for .properties file format
indentation
support for new properties : downloadUrl and changelogUrl
Merge branch 'seb4stien/addon-update-check' of github.com:seb4stien/freeplane into seb4stien-seb4stien/addon-update-check
- make version.properties the default add-on version file
- refactorings