Initial svn import of bridge disbursal code

svn:r12771
Move specs and proposals into doc/ directory.
Separate backend database improvements into their own proposal.
Move XXX-bridgedb-database-improvements.txt and history into torspec.git.

The command used to filter the file and its commit history from
bridgedb.git was:

  $ git filter-branch -f --index-filter \
      'git rm --cached -qr -- . && git reset -q $GIT_COMMIT -- doc/proposals/XXX-bridgedb-database-improvements.txt' \
      --prune-empty \
      --parent-filter 'ruby /home/isis/scripts/git-rewrite-parents.rb $@' \
      --tag-name-filter cat -- --all

with the `git-rewrite-parents.rb` script, taken from
http://www.spinics.net/lists/git/msg177988.html, containing:

  old_parents = gets.chomp.gsub('-p ', ' ')
  if old_parents.empty? then
    new_parents = []
  else
    new_parents = `git show-branch --independent #{old_parents}`.split
  end
  puts new_parents.map{|p| '-p ' + p}.join(' ')
Merge branch 'db-spec_1' into bridgedb-database-improvements_1
Move bridgedb.git:/doc/bridge-db-spec.txt → torspec.git:/bridgedb-spec.txt.

The git filter-branch command used on the bridgedb.git repo was:

  $ git filter-branch -f --index-filter \
      'git rm --cached -qr -- . && git reset -q $GIT_COMMIT -- doc/bridge-db-spec.txt' \
       --prune-empty \
       --parent-filter 'ruby /home/isis/scripts/git-rewrite-parents.rb $@' \
       --tag-name-filter cat -- --all
Merge remote-tracking branch 'bridgedb/bdb-spec' into bridgedb/1606-bridgedb-spec
Merge remote-tracking branch 'isis/bridgedb-database-improvements_1'
Give proposal 226 a number