[IOT-2259] Windows: Handle Persistent Storage for UWP Apps

[IOT-2259] Windows: Handle Persistent Storage for UWP Apps

Changes to allow UWP apps that use IPCA to handle Persistent
Storage:
- Updated the SConscripts to point to store LIBS
- Added a UWP_APP env variable to enable building store DLLs
- Disabled gtest and other tests when building store DLLs
  because gtest is heavily dependent on win32 APIs and DLLs
- Add code to set the sqlite3 temporary directory when building
  for store DLLs (as required by sqlite3). This temporary
  directory will be the appropriate temp directory.
- Add a platform helper function to get the best application
  path to store the Persistent Storage files. IPCA uses this
  helper function to get the path when opening PS files.
- Add capability to run.bat to build UWP DLLs

Change-Id: Iac3a2c9e9e2fd994b06e964254f2d394b15526aa
Signed-off-by: Ibrahim Esmat <iesmat@microsoft.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/19845
Reviewed-by: Alex Kelley <alexke@microsoft.com>
Tested-by: jenkins-iotivity <jenkins@iotivity.org>
Reviewed-by: Dan Mihai <Daniel.Mihai@microsoft.com>