wiki: redirect everything to go.dev/wiki For #61940.
url updates to go.dev / pkg.go.dev
fix typo
Updated DesignDocuments (markdown)
add SSA Backend proposal
add bootstrap plan
I think the dev.cc branch plan was done in 1.4.
Go 1.5 section
DesignDocuments: recover missed changes.
DesignDocuments: fix formatting for future proposals
DesignDocuments: update.
Wiki data import from Google Code