WIP: Less dlls

This patach tries to move nearly all dlls in lib subfolder. Actually this is "replacing one set of a hacks with another set of a hacks" However this leads to followinf improvements:

• smaller installation size
• 10% smaller installer size
• less confusion during debugging where dll is loading
• a hope (is not achieved yet) for a more clean fix for #267 (closed)
• after 497bc047 meld's directory is added to PATH. And Path on windows is sometimes used for DLLs to. Having many dlls in meld folder gives a greater chance to break some other (maybe actually written wrong, but...) applications
• think that such layout actually more compliant to cx_Freeze design
• easier to spot exes in a installation root (would be useful for publishing zips)

However it is still in WIP state - with MSYSTEM var set to any value - it fails with similar to #267 (closed) at the python init stage:

Python path configuration:
  PYTHONHOME = (not set)
  PYTHONPATH = (not set)
  program name = 'S:\meld-windows\ICONS-AND-DLLS-Meld-3.21.1.mingw\Meld.exe'
  isolated = 0
  environment = 0
  user site = 1
  import site = 0
  sys._base_executable = 'S:\\meld-windows\\ICONS-AND-DLLS-Meld-3.21.1.mingw\\Meld.exe'
  sys.base_prefix = ''
  sys.base_exec_prefix = ''
  sys.executable = 'S:\\meld-windows\\ICONS-AND-DLLS-Meld-3.21.1.mingw\\Meld.exe'
  sys.prefix = ''
  sys.exec_prefix = ''
  sys.path = [
    'S:\\meld-windows\\ICONS-AND-DLLS-Meld-3.21.1.mingw\\lib\\library.zip',
    'S:\\meld-windows\\ICONS-AND-DLLS-Meld-3.21.1.mingw\\lib',
  ]
Fatal Python error: init_fs_encoding: failed to get the Python codec of the filesystem encoding
Python runtime state: core initialized
Traceback (most recent call last):
  File "<frozen zipimport>", line 520, in _get_decompress_func
ImportError: DLL load failed while importing zlib: The specified module could not be found.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<frozen zipimport>", line 568, in _get_data
  File "<frozen zipimport>", line 523, in _get_decompress_func
zipimport.ZipImportError: can't decompress data; zlib not available

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<frozen zipimport>", line 241, in load_module
  File "<frozen zipimport>", line 709, in _get_module_code
  File "<frozen zipimport>", line 570, in _get_data
zipimport.ZipImportError: can't decompress data; zlib not available

Also this may break windows7 without update KB2533623 (AddDllDirectiry improvements, released in 2011). Without MSYSTEM var - tested on updated win7 and on win10.

I'm publishing mostly to share some progress in this area (and to save overall time if somebody else would investigating the same area)