fixed up tlv serialisers:
 - Added RsTvlUnit: public RsTlvItem, which handles some of the infrstructure.
 - made TlvSize() SetTlv() and print() const.
 - split rstlvtypes into its bits and cleaned up header files.
 - added templated RsTlvList, imilar to cyrils id one.
 - removed GXS_GEN_TESTNET
 - cleanedup rsserviceids.



git-svn-id: http://svn.code.sf.net/p/retroshare/code/trunk@7215 b45a01b8-16f6-495d-af2f-9b41ad6348cc