Add cmake cache variables to configure remote deps

The main reason of this change is to place URLs and Git Tags of remote
dependencies at the top of CMakeLists.txt

Another outсome is that the user will be able to adjust these settings
easily.

CMakeLists.txt

@@ -3,13 +3,23 @@ project(exple_cmake_build CXX)
 
 option(DOWNLOAD_DEPS "Enable automatic download of dependencies" ON)
 
+set(COMMON_LIB_URL "http://tesla.parallel.ru/vonopr/explelibx-common.git"
+  CACHE STRING "Git repository URL of the downloaded 'explelibx-common' dependency; used if DOWNLOAD_DEPS enabled")
+set(COMMON_LIB_TAG "e45b60782a6414125c7300d9b7a77d34a8404d6e"
+  CACHE STRING "Specify the branch name, tag name or commit hash of the downloaded 'explelibx-common' dependency; used if DOWNLOAD_DEPS enabled")
+
+set(GRID_LIB_URL "http://tesla.parallel.ru/vonopr/explelibx-mgrid.git"
+  CACHE STRING "Git repository URL of the downloaded 'explelibx-mgrid' dependency; used if DOWNLOAD_DEPS enabled")
+set(GRID_LIB_TAG "c345859b9ebca2227e3b3faea4cc2380fdbb054f"
+  CACHE STRING "Specify the branch name, tag name or commit hash of the downloaded 'explelibx-mgrid' dependency; used if DOWNLOAD_DEPS enabled")
+
 # download dependency 'explelibx_common' or find it locally
 if (DOWNLOAD_DEPS)
   include(FetchContent)
   FetchContent_Declare(
     explelibx_common
-    GIT_REPOSITORY http://tesla.parallel.ru/vonopr/explelibx-common.git
-    GIT_TAG e45b60782a6414125c7300d9b7a77d34a8404d6e)
+    GIT_REPOSITORY "${COMMON_LIB_URL}"
+    GIT_TAG "${COMMON_LIB_TAG}")
   FetchContent_MakeAvailable(explelibx_common)
   set(COMMON_DIR "${explelibx_common_SOURCE_DIR}")
 else()
@@ -29,8 +39,8 @@ if (DOWNLOAD_DEPS)
   include(FetchContent)
   FetchContent_Declare(
     explelibx_mgrid
-    GIT_REPOSITORY http://tesla.parallel.ru/vonopr/explelibx-mgrid.git
-    GIT_TAG c345859b9ebca2227e3b3faea4cc2380fdbb054f)
+    GIT_REPOSITORY "${GRID_LIB_URL}"
+    GIT_TAG "${GRID_LIB_TAG}")
   FetchContent_MakeAvailable(explelibx_mgrid)
   set(GRID_DIR "${explelibx_mgrid_SOURCE_DIR}")
 else()