usage of SPDX-License-Identifier within POCO project

Work with software from multiple sources with different licenses is a heavy thing as long as license is not easily accessible in a programmers way. That's why I suggest to introduce the following onliner for the license within individual source files instead of the full license text.

SPDX-License-Identifier:  BSL-1.0

This enables machine processing of license information based on the SPDX License Identifiers that are here available: http://spdx.org/licenses/

A popular project using SPDX-License-Identifier is U-Boot, see here: http://git.denx.de/?p=u-boot.git;a=blob;f=Licenses/README;hb=HEAD

All the best!
-roger
;-r