Merge pull request #30 from fabioz/master

Exporting packages so that other plugins can use the startexplorer API
drag'n'drop install button
add text to install button
optional Maven/Tycho build; 100% ready for Travis CI
old id substituted
Merge pull request #35 from Nodeclipse/master

optional Maven/Tycho build; 100% ready for Travis CI
Add missing categoryId to "show in file manager" action. Closes #33.
Provide command set for Mate. Closes #34.
URL handling (closes #28, I think, but need to do a bit more testing,
especially on windows)
Update
Auto-detect Linux MATE (closes #34)
Change log up
Update
Update help
Release 1.5.0
Release 1.5.0
Update poms for 1.5.0
Update README.markdown

1.5.0 already published, so not "upcoming".
More tasks for release
Fix for problems when editor shows a class file from Jar. Related to
#38.