extract MavenCentral interface
cached MavenCentral
change used Hashtable to HashMap in CachedMavenCentral implementation
fix theoretically possible cache id conflict
fix CachedMavenCentral compatibility with MavenCentral interface
Merge pull request #952 from psliwa/performance-bust

Extract MavenCentral interface + cache support implementation for MavenCentral