zf1s/zf1: require php extensions in dev only

[falkenhawk]

followup on #133, #128 (comment)

It is probably too restrictive to have them listed in require section in the root composer.json file.

Composer will complain that an extension is not installed, e.g. ext-ldap for Zend_Ldap, even if it's not needed i.e. a project is not using Zend_Ldap at all.

> composer require zf1s/zf1

  [InvalidArgumentException]                                                                                  
  Package zf1s/zf1 has requirements incompatible with your PHP version, PHP extensions and Composer version:  
    - zf1s/zf1 1.15.0 requires ext-ldap * but it is not present.    

Due to the nature of zf1, you may never need some of the extensions, as long as you do not use components which require them. But when you start using them, those components themselves should throw errors that required extensions are not installed.

Moved to require-dev to ensure they are installed when running tests on dev/CI.

I've considered adding them to suggest section but imo composer might spam too much with irrelevant information, when installing zf1s/zf1 package.

ref: #128 (comment)

[glensc]

require-dev is indeed better than suggests, as then the dependencies can be enforced in ci

[marcing]

I approve this change.