Added license

Derived from first page of OGC's pdf version of the draft specification
Update LICENSE.md
added OGC logo
Update README.md
added preamble information
Added richer overview
Tightening up the readme
Tweaks to wording
Added 'sample implementations' section.
link tweak
Added link to base
Update 3_tiles.md
Link tweaks
updated for r8
Merge branch 'master' of https://github.com/opengis/geopackage
finished annex b to match r8
added note that annexes aren't done
Update README.md
Changed around to focus on user, not swg member.

Added lots of github tips, moved things around.
Fix name of table mentionned in Req 12

spatial_ref_sys view has a srid column, whereas gpkg_spatial_ref_sys has srs_id. The fix makes it consistant with the description of "Table 3: Contents Table or View Definition"