Add intervalometer filter for automatic exposure control

Implements YASS-inspired automatic exposure control for IDS uEye cameras.
The intervalometer filter analyzes video brightness in real-time and
smoothly ramps camera exposure and gain settings during changing light
conditions - ideal for sunset/sunrise time-lapse photography.

Key features:
- Automatic exposure ramping (0.85-1.24ms configurable range)
- Automatic gain control (0-52 configurable range)
- Real-time brightness analysis (GRAY8, GRAY16, RGB, BGR, BGRA)
- YASS-inspired ramping algorithm (exposure priority, then gain)
- Configurable ramp rates (VSlow/Slow/Medium/Fast/VFast)
- Exposure compensation (±4 stops)
- CSV logging of exposure parameters
- Direct GObject property control (no message bus overhead)

Technical implementation:
- GstBaseTransform filter for in-place processing
- Discovers upstream camera element by name
- Controls camera via g_object_set() for synchronous updates
- Frame-by-frame brightness calculation with format support

Files added:
- gst/intervalometer/gstintervalometer.c: Main implementation (734 lines)
- gst/intervalometer/gstintervalometer.h: Header with structure definitions
- gst/intervalometer/CMakeLists.txt: Build configuration
- gst/intervalometer/README.md: Comprehensive documentation

Files modified:
- gst/CMakeLists.txt: Added intervalometer subdirectory
- build.ps1: Added intervalometer to build and deployment pipeline

Usage example:
  gst-launch-1.0 idsueyesrc name=cam ! \\
    intervalometer enabled=true camera-element=cam \\
      exposure-min=0.85 exposure-max=1.24 \\
      gain-min=0 gain-max=52 ramp-rate=medium ! \\
    autovideosink

Inspired by YASS (Yet Another Sunset Script) for CHDK cameras by
waterwingz, based on work by Fbonomi and soulf2.

gst/intervalometer/CMakeLists.txt

@@ -0,0 +1,28 @@
+set (SOURCES
+  gstintervalometer.c
+  )
+    
+set (HEADERS
+  gstintervalometer.h)
+    
+include_directories (AFTER
+  ${ORC_INCLUDE_DIR})
+
+set (libname gstintervalometer)
+
+add_library (${libname} MODULE
+  ${SOURCES}
+  ${HEADERS})
+  
+target_link_libraries (${libname}
+  ${ORC_LIBRARIES}
+  ${GLIB2_LIBRARIES}
+  ${GOBJECT_LIBRARIES}
+  ${GSTREAMER_LIBRARY}
+  ${GSTREAMER_BASE_LIBRARY}
+  ${GSTREAMER_VIDEO_LIBRARY})
+  
+if (WIN32)
+  install (FILES $<TARGET_PDB_FILE:${libname}> DESTINATION ${PDB_INSTALL_DIR} COMPONENT pdb OPTIONAL)
+endif ()
+install(TARGETS ${libname} LIBRARY DESTINATION ${PLUGIN_INSTALL_DIR})