Refactor installation of PHP extensions

[J0WI]

No functional changes, except from PECL extensions that are now fixed (where just disabled before).

[J0WI]

As a side effect, this also reduces the image size.

[J0WI]

Since #59 has not been touched for a while, I merged this minor change into my branch.

[pierreozoux]

This totally changes the codestyle.
Can you stick to the original codestyle that is used in official docker images?

Thanks :)

[J0WI]

@pierreozoux I changed the code style to be consistent to other containers form the docker-library.
I can revert this if it's required.

[tianon]

@pierreozoux see docker-library/php#556 and docker-library/wordpress#267 for similar conversions elsewhere

[pierreozoux]

Ah ok, sorry didn't see that it evolved.
I'm not really for that or this codestyle, just being consistent.

I added the TLS in the mean time, so it is not required anymore.
I'll take care of merging it without the TLS part!

Thanks a lot for your contribution!

[pierreozoux]

Sorry, I didn't want to bother you, so I just refactored and merged, but your name disappeared :/
I tried to ammend the author, without much success. If you knwo a better, let me know, and I'll do it!
All the best! And thanks for your contribution!

[pierreozoux]

@J0WI I merged your changes, but I have this issue:
https://api.travis-ci.org/v3/job/343342347/log.txt

Could you take a look please?
in the mean time, I'll revert your PR, so you can recreate one, and this way we'll fix our authorship issue :)

[J0WI]

Re-opened in #80.