CPSs: Improve template and ensure existing CPSs align (#1128)
* CPS-0009 add missing copyright and license
* CPS-0007 add missing section and fix heading levels
* CPS-0003 add missing license
* CPS-0008 add header field
* CPS-0013 fix header
* update CIP-9999 and CPS template for improved header
* CPS-0003 update header
* CPS-0005 update header
* CPS-0007 update header
* CPS-0008 update header
* CPS-0009, CPS-0010, CPS-0011 update header
* CPS-0012, CPS-0013, CPS-0014 update header
* CPS-0016 - CPS-0022 update header
* CPS-0017 remove implementors field from header
* CPS-0017 remove white space from header
* Capitalise Use Case header throughout CPSs
* Capitalise Open Questions header throughout CPSs
* tweak discussion label naming in CPS-0003 header
* fix labels in header of CPS-0003
* reorder CPS header fields
* CPS-0020 remove bold from references section heading
* CPS-0020 remove trailing whitespace from heading
