Fix .gitignore to avoid ignoring prebuilt libraries.

Also, generally clean-up the .gitignores and farm off separate versions for the NuttX/Apps directories to keep things tidy.

.gitignore

-.built
-.context
-*.context
-*.bdat
-*.pdat
-.depend
-.updated
-.config
-.config-e
-.version
-.project
-.cproject
-apps/builtin/builtin_list.h
-apps/builtin/builtin_proto.h
-Make.dep
-*.pyc
-*.o
-*.a
 *.d
-*~
+!ROMFS/*/*.d
+!ROMFS/*/*/*.d
+!ROMFS/*/*/*/*.d
 *.dSYM
-Images/*.bin
-Images/*.px4
-nuttx/Make.defs
-nuttx/setenv.sh
-nuttx/arch/arm/include/board
-nuttx/arch/arm/include/chip
-nuttx/arch/arm/src/board
-nuttx/arch/arm/src/chip
-nuttx/include/apps
-nuttx/include/arch
-nuttx/include/math.h
-nuttx/include/nuttx/config.h
-nuttx/include/nuttx/version.h
-nuttx/tools/mkconfig
-nuttx/tools/mkconfig.exe
-nuttx/tools/mkversion
-nuttx/tools/mkversion.exe
-nuttx/nuttx
-nuttx/System.map
-nuttx/nuttx.bin
-nuttx/nuttx.hex
-.configured
-.settings
-Firmware.sublime-workspace
+*.o
+*.pyc
+*~
+.*.swp
+.context
+.cproject
 .DS_Store
-cscope.out
-.configX-e
-nuttx-export.zip
+.gdbinit
+.project
+.settings
+.swp
 .~lock.*
+Archives/*
+Build/*
+core
+cscope.out
 dot.gdbinit
+Firmware.sublime-workspace
+Images/*.bin
+Images/*.px4
 mavlink/include/mavlink/v0.9/
-.*.swp
-.swp
-core
-.gdbinit
-mkdeps
-Archives
-Build
-!ROMFS/*/*.d
-!ROMFS/*/*/*.d
-!ROMFS/*/*/*/*.d

apps/.gitignore

+*.a
+*.bdat
+*.pdat
+.built
+.config
+.depend
+.updated
+builtin/builtin_list.h
+builtin/builtin_proto.h
+Make.dep

nuttx/.gitignore

+*.a
+.config
+.config-e
+.configX-e
+.depend
+.version
+arch/arm/include/board
+arch/arm/include/chip
+arch/arm/src/board
+arch/arm/src/chip
+include/apps
+include/arch
+include/math.h
+include/nuttx/config.h
+include/nuttx/version.h
+Make.defs
+Make.dep
+mkdeps
+nuttx
+nuttx-export.zip
+nuttx.bin
+nuttx.hex
+setenv.sh
+System.map
+tools/mkconfig
+tools/mkconfig.exe
+tools/mkversion
+tools/mkversion.exe