Add TlsHelper (designed to be used with sks-keyservers.net)

We can't use the AndroidPinning library for this, because it requires the certificate to be signed using a system CA, sks-keyservers.net uses there own CA
Fixed Issue #683 which caused OK to crash upon importing keys which contain percent signs.
Merge branch 'master' of https://github.com/da-kid/open-keychain
Merge pull request #684 from da-kid/master

Fix of #683
Remove dnsjava module
Add minidns submodule
Switch to dnsjava
Add TlsHelper (designed to be used with sks-keyservers.net)

We can't use the AndroidPinning library for this, because it requires the certificate to be signed using a system CA, sks-keyservers.net uses there own CA
Add hkps support for sks-keyservers.net
Few fixes on hkps

TODO: Fix add as well
Merge branch 'hkps-by-default' of github.com:mar-v-in/open-keychain into hkps-by-default
Merge pull request #686 from mar-v-in/minidns

Use minidns instead of dnsjava
Rewrote hkp add to work with hkps as well.
Also removes HttpClient dependency (deprecated for android)
Use URLEncoder instead of Uri.encode
Update Keyservers to use hkps as needed
Fix sks-keyservers.net sub pool
Merge branch 'master' into hkps-by-default
Rename registered apps to apps
Fix for #687
Merge submodules