Plugins build system upgrade

We're working on upgrading the build system on all official plugins. This effort will enable us to have better plugin integration into different system and is an important upgrade to clean up various dependencies that proved to be problematic (such as freenet-ext).

As a summary:

Plugins already ported:

• https://github.com/freenet/plugin-KeyUtils
• https://github.com/freenet/plugin-UPnP2
• https://github.com/freenet/plugin-FlogHelper
• https://github.com/freenet/plugin-Freetalk

Plugins being ported:

• https://github.com/freenet/plugin-Library
  • https://github.com/freenet/plugin-Library/pull/17
• https://github.com/freenet/plugin-UPnP
  • https://github.com/freenet/plugin-UPnP/pull/12
• https://github.com/freenet/plugin-sharesite
  • https://github.com/freenet/plugin-sharesite/pull/3

Port pending:

• https://github.com/freenet/plugin-Freemail
• https://github.com/freenet/plugin-Freereader
• https://github.com/freenet/plugin-Spider