Support for non standard vcsTags in Bintray

[szpak]

Currently when the new version is uploaded to Bintray the vcsTag field is not set and Bintray uses plain version (e.g. 1.3.2) as a tag name. With more complicated release tag patterns (e.g. release/1.3.2) it is required to specify that explicit (with bintray.pkg.version.vcsTag).