Make nuSOAP library location configurable

I though it would be easier, but it took 11kb to do the change. I have included some new error checking because of the change (it could happend that library is configured but deleted, or is installed but not configured, or is not installed neither configured, or installed but configured in a wrong directory). To make requirements checks available during installation I included the .install file, so I also created the uninstall hook to remove the module variables.

The module looks for installed nusoap files within sites/all and sites/%current_site, in the hope of finding at least one version. In the documentation it will be a good point to use /sites/all/plugins to install nuSOAP library there, so other modules may still use it, not having to install nuSOAP twice.

I just left the hook_init to make cyphering available for now, but I guess this will be removed. Cyphering, even if used by some services has nothing to do with soapclient module.

Once this patch gets reviewed and commited, the next steps will be:
#408360: NuSOAP project code should not be in CVS
#581060: Cyphering is not being in use
#408362: Directory structure not correct

mm I forgot to remove some globals. Also I have include more error checking.

some minor changes to the patch.

Patch reviewed by Peter Bex:
- English typo: any to none
- Preference is given to sites/%current_site and then to sites/all when searching for installed nuSOAP Libraries

Commited to 6.x-1.x-dev branch.