http-client taken out of zorba core

added tidy dependency
Use PROJECT_SOURCE_DIR instead of CMAKE_SOURCE_DIR to support building inside
a Zorba project. Also (temporarily?) change project name to "http-client"
to match the directory name, as currently required by in-Zorba build.
Working http-client module
Added How to Build Documentation
Fix project name; remove SET_EXTERNAL_MODULE_CONFIG() (done automatically by
ZorbaUse now); add two expected failures.
XQDoc rework.
Now zorba and each external module have two build targets: xqdoc-xml and xqdoc. 
xqdoc-xml is to generate the xml from xqdoc information.
xqdoc target is to generate the final html from the intermediary xml.
Zorba's xqdoc depends on the xqdoc-xml from zorba and all external modules.
You can also build the xqdoc target for a specific external module, and generate only its documentation. If the external module is built in zorba project, then the zorba internal modules' xqdoc is always generated.
fix for bug #3304417. The expected result changed; the headers returned by the http server were reordered.
removed curl dependencies from zorba core
new DECLARE_ZORBA_MODULE macro for all external modules + version 1.0 for all modules
http-client error namespace cleanup and put base64 module back to core
Added DECLARE_ZORBA_SCHEMA() and cut over internal and external modules to
use it. Enhancements to DECLARE_ZORBA_MODULE(), including better API with
explicit parameters, and shorter target names to help Windows 260-character
path limitations.
Moved non-W3C annotations to the Zorba namespace. Unknown annotations will raise errors.
Restructure DECLARE_ZORBA_MODULE()/DECLARE_ZORBA_SCHEMA() to not create a ton
of mini-targets, to help clean up MSVC projects. Required introduction of
DONE_DECLARING_ZORBA_URIS() which is added to all module projects and Zorba.
Numerous changes from Juan for 0-configuration on Windows and Windows
installer issues. Also some tweaks from me for install path issues.
Removing stale INSTALL directives from external modules.
Fixed scripting issues with http-client tests.
fixed problem with wrong usage of scripting
XQuery version changes:
- Added XQuery version declarations for all the modules (part of the Zorba core or not).
- fixed the test "moduleDocumentation" that checks if all the modules are well documented:
  - this test used to check only the Zorba core modules: now it also checks the external modules.
  - added a new rule that makes sure all modules have a XQuery version declarations.

XQDoc changes:
- documented some XQDoc variables, params and return values that were missing.
- added support for XQuery version and Encoding in the Zorba XQDoc.
- added a new part called "XQuery version and Encoding for this module:" as the last lines in the module description of the XQDoc documentation.
fixes for Mantis bug 0000090
Adding a automatic test case for each declared module which imports the module,
to ensure it compiles and can be imported. Fixed several bugs which were
revealed by those tests. Also, changed variable ZORBA_EXE_SCRIPT to
ZORBA_EXE and made this variable available in ZorbaConfig for other projects.