Fix bug: allow removing torrents from own channel

Fixes #1019
Merge pull request #1063 from whirm/backport_remove_channel_torrent_fix

Fix bug: allow removing torrents from own channel
Add python-crypto to the list of dependencies
Merge pull request #1068 from whirm/update_deps

Add python-crypto to the list of dependencies
Refactored optional_crypto, removed the optional part.
* additionally switched to default seed for gmpy rand method
Fixup
No more privatesemantic, privatesearch, and privatesocial.
Only tunnelcrypto remains
Fixup
Not using custom DH implementation anymore, switched to DH included in
M2Crypto/OpenSSL.
Old version which includes custom DH renamed to OldTunnelCrypto.
No more gmpy rand
Testing ecelgamal encrypt/decrypt in performance loop
Merge pull request #1069 from whirm/improve_crypto_for_next

Improve crypto for next
Make TunnelCommunity loading configurable and disabled by default
Opt-in dialog for TunnelCommunity
Temporary ugly hack to work around #1067 for v6.4.1 release
Merge pull request #1064 from whirm/anontunnel_optin

Make TunnelCommunity loading configurable and disabled by default
Update windows packager for new curves.ec location
Merge pull request #1071 from whirm/fix_windows_packaging

Update windows packager for new curves.ec location
Fix the NSI script for the new curves.ec location
Merge pull request #1072 from whirm/fix_windows_packaging

Fix the NSI script for the new curves.ec location