LYN-3069 Revert some 3rdparty changes and address issue (#185)

* renaming and organizing files

* removed unused files

* Removing unnecessary file

* moved file

* reverting movement of 3rdparty associations from gems to global

* removing unnecessary calls to ly_add_external_target_path

* fixing install prefix of ci_build

* Fixes to get 3rdparties declared in gems to be installed

* Allowing to install just one configuration

* Adding empty line at the end

* removing commented code

* setting IMPORETD_LOCATION_<CONFIG> and defaulting IMPORTED_LOCATION to the profile config in case other configs are not installed

Gems/Atom/Asset/ImageProcessingAtom/3rdParty/cubemapgen.json

@@ -1,9 +0,0 @@
-{
-    "name": "cubemapgen",
-    "source": "@GEM@/External/CubeMapGen",
-    "description": "CubeMapGen",
-    "defines": [],
-    "lib_required": "False",
-    "includes": [""]
-}
-

Gems/Atom/Asset/ImageProcessingAtom/CMakeLists.txt

@@ -10,6 +10,4 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 #
 
-ly_add_external_target_path(${CMAKE_CURRENT_LIST_DIR}/3rdParty)
-
 add_subdirectory(Code)