Directory reorganization: move website source files into src/ directory

[davorbonaci]

This should make the site repository much cleaner.

R: @francesperry @dhalperi
CC: @jbonofre

[asfbot]

Refer to this link for build results (access rights to CI server needed):
https://builds.apache.org/job/beam_PreCommit_Website_Test/27/

[asfbot]

Refer to this link for build results (access rights to CI server needed):
https://builds.apache.org/job/beam_PreCommit_Website_Stage/73/

Jenkins built the site at commit id 3312bcd with Jekyll and staged it here. Happy reviewing.

Note that any previous site has been deleted. This staged site will be automatically deleted after its TTL expires. Push any commit to the pull request branch or re-trigger the build to get it staged again.

[asfbot]

Refer to this link for build results (access rights to CI server needed):
https://builds.apache.org/job/beam_PreCommit_Website_Test/28/

[asfbot]

Refer to this link for build results (access rights to CI server needed):
https://builds.apache.org/job/beam_PreCommit_Website_Stage/74/

Jenkins built the site at commit id cc98265 with Jekyll and staged it here. Happy reviewing.

Note that any previous site has been deleted. This staged site will be automatically deleted after its TTL expires. Push any commit to the pull request branch or re-trigger the build to get it staged again.

[jbonofre]

LGTM

[davorbonaci]

Thanks @jbonofre; merged.