Logger pattern as vector of `[...]` blocks

Plugin can only replace current default logger pattern of PDI logger. This way plugins patterns cannot coexist. To solve the issue pattern can be created from vector of [...] blocks.

For example vector of: [[%T], [%{MPI_COMM_WORLD_rank:06d}], [%n], *** %^%l%$: %v]

would resolve in: [%T][%{MPI_COMM_WORLD_rank:06d}][%n] *** %^%l%$: %v pattern.