www/foreign-cdm: Reorganize the port.

• Do not install anything into LINUXBASE.
• Add an environment setup script.
• Remove pkg-plist.
• Remove original Google Widevine files from this port to avoid licensing problems. Users are expected to install www/linux-widevine-cmd on their own.

(cherry picked from commit 50f7afc62558db975f4815f6b2422f52a7cb0e0f)