Release 5.8.0

Signed-off-by: Hiroshi Miura <miurahr@linux.com>

5.7.0 release

5.6.0 release

5.5.0 release

[omegat-org#1551] Migrate packages from Bintray to Maven Central

https://sourceforge.net/p/omegat/feature-requests/1551/

5.4.3 release

Correct enhancement count for 5.4.2

Bump to 5.4.1