Added method to get escape characters to SQLDialect. Added AbstractSQLDialect to return char.UNASSIGNED as default escape character. Made SQLDialects extend AbstractSQLDialect. Added postgres escape characters to PostGISDialect.
make use of escape characters provided by SQLDialects in #getUnescapedColumnMetadata
Merge branch 'feature/escapingWorkspaceInitialization-1558' of https://github.com/lat-lon/deegree3 into feature/escapingWorkspaceInitialization-1558